Abstracts of papers presented at Low Frequency 2002

Below are a list of all the papers in the same order as presented at the conference.

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An investigation of the perception thresholds of complex low frequency noises: influence of spectrum

Summary

Perception thresholds of complex low frequency noises have been investigated in a laboratory experiment. Sound pressure levels that were just perceptible by subjects were measured with three complex noises and three pure tones. The complex noises had a flat constant spectrum over the frequency range 2 to 10, 20, or 40 Hz and decreased with rate of 15 dB per octave at higher frequencies. The frequencies of the pure tones used in this study were 10, 20 and 40 Hz. The perception thresholds were obtained with an all-pass filter, one-third-octave band filters, and the G frequency weighting defined in ISO 7196. The G-weighted sound pressure levels obtained were compared with 100 dB which is described in ISO 7196 as the G-weighted level corresponding to the threshold of sounds in the frequency range 1 to 20 Hz. The perception thresholds of the pure tones measured in this study were comparable to the results available in various previous studies. The one-third octave sound pressure levels obtained for the thresholds of the complex noises tended to be lower than the measured thresholds of the pure tones. The G-weighted sound pressure levels obtained for the thresholds of the complex noises appeared to be lower than 100 dB.

Thresholds and acceptability of low frequency pure tones in sufferers

Summary

To investigate sensory thresholds and subjective evaluations of low frequency pure tones in noise sufferers who complain of annoying environments in their everyday life, sound pressure levels of sensory thresholds and subjectively acceptable maximum SPL levels for a living room were measured in a low frequency chamber. These measurements were made by a psychophysical experiment using eleven pure tones at low frequencies from 10Hz to 100 Hz as stimuli, and a psychophysical method of subject adjustment was used for the measurement. Twelve members of the noise-sufferer society in Japan participated as subjects (referred to as participants in the following) in the measurement experiment. The results show that all the participants' acceptable maximum sound pressure levels were relatively low, and nearly equal to their sensory thresholds. These results are characteristic of the participants and differ from the previous results obtained from the other adults

Laboratory Determination of Annoyance of Low Frequency Noise

Summary

Test persons listened to eight different environmental low frequency noises and gave their evaluation of the annoyance of the noises. The noises were stationary noise with and without tones, intermittent noise, music, traffic noise and impulsive low frequency noise. The noises were presented at LAeq levels of 20 dB, 27.5 dB and 35 dB. The subjective assessments were compared to objective results from a number of assessment methods for low frequency noise. It was found that the Danish assessment method (Information No. 9/1997 from the Danish EPA) gave the best relation to the subjective assessments. An important property of this method is that it includes a 5 dB penalty in case of impulsive noise.

Loudness of structure borne sound heard directly by ear put on vibrating structure

Summary

Putting an ear close to a vibrating structure like a wall or a floor, we are able to hear structure-borne sounds clearly, but the loudness of such sounds has never been studied quantitatively. In this study, subjective experiments were carried out in order to obtain the relationship between loudness and the vibration amplitude of the ear's contact surface at low audible frequencies. The main result of this study is that the loudness of a structure-borne sound is almost equal to that of an air-borne sound with a sound pressure level 20 dB higher than the vibration velocity level (ref=5´10-8 m/s) of the surface. According to this result, the loudness of the structure-borne sound heard directly can be evaluated as a sound pressure level derived from the measured vibration amplitude of the structure.

Psychological analysis of sufferers on noise/low frequency noise and relation between brain structure and psychological response

Summary

In Japan there are two kinds of low frequency noise (LFN) problems. One is that LFN can be heard directly and the other is the rattling of windows. Authors met about 100 complainants on noise or low frequency noise. We try to analyze the complainants' mind and explain the mechanism of these problems.
We show some real cases of low frequency noise (LFN) problems. We analyzed their minds. Their minds have three layers. The 1st layer is the basic desire for survival and good life etc. The 2nd layer is their personality or consideration obtained by their experience and the 3rd layer is the movement, speech or action etc. Many complainants lack of the 2nd layer on noise or low frequency noise and their movement and reaction against LFN or noise appeared directly from the 1st layer without consideration of the 2nd layer.
In the brain of a human being, pleasantness or unpleasantness is judged or felt by limbic system of brain. By the survey the relation between the reaction and the brain structure is shown.

Study on the masking of low frequency sound

Summary

Components of complex tone are not separately heard but are heard as one frequency sound in low frequency area. It is difficult to distinguish the component from the complex tone with over two kinds of component. Hearing of complex tone could be connected with masking effect, so the masking effect of low frequency sound was investigated. Pure tone, complex tone and band noise were used as a masker. In results, the amount of masking are small when the frequency of masked sound is lower than the frequency of masker. The amount of masking increases as the frequency of masked sound increases. The frequency characteristic of masking by pure tone is similar to that of masking by band noise. There were a few subjects whose masking values are negative.

Low frequency sound as a navigational tool for people with visual impairments

Summary

For decades, a mistaken assumption in the habilitation of travel for people with visual impairments has been that the use of "echolocation" is a dominant feature of acoustic information for the guidance of locomotion. This paper outlines a theoretical model of acoustic information available in many travel situations. The acoustic information consists of a build up of low frequency sound along large structures such as walls. Useful frequencies are low enough that the experience of this build up is often one of feeling rather than hearing. Experimental validation of this model was accomplished by having participants with visual impairments walk along walls with varying types of auditory occlusion and through laboratory based manipulations of acoustic information. Results indicate that the model is appropriate. Useful acoustic information appears to extend up to 1 m from a wall. There is strong evidence that participants make use of binaural information, gauging the similarity of acoustic information reaching each ear to maintain orientation to a wall. Motion through the sound field near the wall makes the information more useful but it is unclear whether motion in certain directions or conditions is more useful than others.

Low frequency noise annoyance. Results of a UK survey into the incidence and intervention methods reported by environmental health officers.

Summary

The common theme to which many LFN researchers subscribe to is that there is a phenomenon that is consistently under-rated in terms of its status as an environmental pollutant. The difficulties surrounding the development of an effective and systematic approach to the quantification of LFN incidence and its associated impact have centred upon source detection, location and annoyance loading. Moreover, the quantification of each and all of these aspects has been complicated by the combination of significant 'individual differences' in sensitivity to LFN combined with the relatively low sound pressure levels (SPLs) associated with disturbance, annoyance and stress.

Inadequate standards currently applied by local authorities to determine Statutory Nuisance from LF and infrasound

Summary

This paper examines some of the barriers experienced by those who complain to their local authorities about low frequency noise (LFN).
The extent of the problem will be examined by presenting data from a survey of UK Environmental Health Officers (EHO's) on their use of weighting with low frequencies, and by quoting from my own experience.
The root causes of the problem will be identified, and solutions suggested.

When quiet means loud - experiencing Low-frequency Sound? - a case study

Summary

An independent non-specialist observer (the subject) has experienced troublesome effects of annoying sound, especially at night, together with a wide range of associated physical and other effects. He has sought to identify the frequency(ies) responsible for the phenomenon. Through analysis of the sound spectrum recorded at a wide range of geographic locations, exaggerated perceptions of low-amplitudes of low frequencies have been implicated and indications are that the potential sources are varied. A critical feature of the annoyance appears to be the tonal nature and "character" of the sound experienced and its relationship to the sound in the ambient spectrum. It is also possible that the mood or state of mind of the individual may play a part in the intensity of the experience.

All data are displayed in line graphs. This method has been used for ease of comparison between one set of readings and another. However the lines joining the point values for each frequency have in themselves no relevance beyond enhancing the visual appreciation of the data.

Personality and Annoyance by Low & Mid Frequency Environmental Noise

Summary

The three types of response in the population environmental noise, the "Sensitive", the "Insensitive" and the "Neutral"(Langdon, 1985) are three groups of people of approximately equal size. This behaviour is predictable and described by the personality of those working from the three Centres of the Enneagram: The Gut, the Head and the Heart respectively. Questionnaires determining a) noise annoyance sensitivity and b) personality in terms of Enneagram Centre and Type were administered to 107 adults, of whom 63 females (average age 53 years) and 44 males (average age 55 years). There were significant differences, in response to noise of those operating from the Gut(most sensitive) and Heart Centres, to those operating from the Head Centre (least sensitive). Also a tentative hierarchy of noise sensitivity put the "Perfectionist" and the "Artist" Types One and Four respectively, first whilst the least sensitive was the "Observer" Type Five. There were also found to be gender differences in noise sensitivity with females bothered more frequently than males. Those subjects living in urban areas were also more annoyed than those living in suburban or rural areas. Further work is ongoing and some results have been obtained, using the same two questionnaires, on subjects reporting being affected by low frequency/infrasonic noise.

Assessments of low frequency noise complaints -
a follow-up study 14 years later

Summary

Interviews among a selection of 37 of the 289 Swedish local Environmental Health Authorities (EHA) were undertaken in order to assess the occurrence of complaints on low frequency noise. The study also aimed to evaluate whether the recommendation on low frequency noise, adopted in 1996, was used in assessing low frequency noise and how it was judged by the EHA. The results showed that most complains on low frequency noise were due to noise from fan- and ventilation installations, compressors, music noise and laundry-rooms. According to 46% of the EHA, complaints due to low frequency noise had increased during the last two years, while the same percentage reported no change. The results also showed that most EHA preferred the specific recommendation for low frequency noise, based on third octave band analysis, to previous A-weighted guidelines when assessing low frequency noise.

Nine years of Dutch experience in the evaluation of vibrations in relation to nuisance

Summary

In 1993, the Dutch started to build up experience with their own standard about the evaluation of vibrations in relation to nuisance. The committee that published this standard was very much aware of the complex relation between vibrations and nuisance. In the introduction of this publication the committee already mentioned the future possibility of changing the limiting values due to results of new studies. Nine years later, this vision has turned into reality. The limits have changed. But there are more changes. Changes which the committee did not forsee.

Vibration perception thresholds in healthy subjects assessed by two different methods

Summary

Objectives: Vibration perception thresholds (VPTs) differ depending on the equipment and methods of measurement, and they are different in many European countries. In the pre-accession to EC, it is important to adjust Polish hygienic standards, including these regarding exposure to vibration, to the international one. The study was designed to compare VPTs in healthy subjects using two different methods of measurement. The first one was a standard technique used currently in Poland and the second one was based on the principles of the International Standard ISO/FDIS 13091-1(2001).

Methods: The study comprised 187 healthy subjects, aged 17-57 years, not occupationally exposed to vibration. Both measurements of VPTs were performed using the same equipment (P-8, EmsonMat). The main differences in methodology between standard method and the method adjusted to ISO included: different mode of stimuli presentation (ascending vs. Bekesy), frequency range applied (63-500 Hz vs. 4-125 Hz), probe contact force (larger in standard method), probe diameter (12 mm vs. 5 mm) and surface (plane vs. rough).

Results: The mean VPTs differed significantly between the standard and ISO method at the overlapping frequencies, with the differences varied from 2.2 to 6.4 dB at frequencies 125 and 250, respectively. The correlation between the thresholds obtained by two methods at these frequencies was not high (correlation coefficients about 0.6), although statistically significant. In the ISO method, the best VPTs were found at 4 and125 Hz. There was a poor correlation between the utmost frequencies (i.e. 125 and 4 Hz) and rather high between adjacent frequencies (i.e. 25 and 32 Hz). Age, weight and height were significant covariates in both measurements. The model to calculate the normative values of VPTs adjusted for explanatory factors were setting up in this study.

Conclusions: The VPTs differ depending on a method of measurement. In order to perform international cohort studies there is a need to establish a unified standardised method of vibrotactile sense assessment.

Measurement of human body surface vibration induced by complex low-frequency noise

Summary

To clarify mechanical responses of the human body to airborne vibration, six male subjects were exposed to eight kinds of low-frequency noise stimuli: white noise, two pure tones (31.5 and 50 Hz) and five complex noises composed of the pure tones. The vibration induced on the body surface was measured at five locations: the forehead, the right and left anterior chest, and the right and left anterior abdomen. It was found that the vibration acceleration levels of both the 31.5- and 50-Hz components in the chest vibration increased as an approximately linear function of the sound pressure level of each corresponding frequency component in the noise stimulus. No clear interference was found between the 31.5- and 50-Hz components in the chest vibration. Similar characteristics were also found in the vibrations induced at the forehead and abdomen. These findings suggested that within a limited range of frequency and sound pressure level used here, the human body acts as a mechanically linear system in response to airborne vibration by complex low-frequency noise

Study on an effect of whole-body vibration and a measurement in a low frequency range

Summary

Today, the ISO is fixed as the criterion curve evaluated a psychological method on the comfortable and uncomfortable feelings. To this end, suggestion was made it necessary to have data for both the physiological reaction and psychological evaluation of humans at low frequency range.
The purpose of this study is clarify physiological and psychological effects of low frequency horizontal vibration on the whole-body. Heart rate, respiratory rate, salivation and subjective symptoms were measured before starting, 21-min after starting the vibration at a frequency ranging from 0.01 to 0.8 Hz.
It is explained that the frequency and acceleration at which a change of the physiological indications to the baseline is formed was obtained at 21-min.
The results were as follows: Changes in the autonomic nervous system were observed, and the system tended to change from the state of predominance of the parasympathetic nervous system to that of the sympathetic nervous system when frequency exceeded the range 0.4 to 0.8 Hz, during 21-min. Throughout all the process of the measurements, it is imagined that these variations have been caused with respect to the physiological and psychological changes mainly by the frequency, the delay time and acceleration based on the whole-body vibration.

EU Directive on Physical Agents - Vibration

Summary

Vibrations that arouse human health concerns are classified into two main categories: (1) hand-arm vibrations (HAV) and (2) whole-body vibrations (WBV). Hand-transmitted vibration from a power or impact tool affects the upper extremities of the body. WBV affects the entire body and is transmitted from a vibrating seat, bed or floor to a person who is in a sitting, lying or standing position.

The EU Directive April 5, 2002 provides exposure limit and action values for both HAV and WBV. These values have taken into consideration recent advances in knowledge and the political judgement of the Member States so are at variance with the present Health and Safety Executive (HSE) values and the ACGIH TLVs. This paper reviews the development of international standards for vibration and the requirements of the EU Directive.

GROUND VIBRATION GENERATED BY A HARMONIC LOAD MOVING IN A CIRCULAR TUNNEL IN A LAYERED GROUND

Summary

All modes of transport impact on the environment. Although railways are seen as environmentally advantageous in many ways, the issues of noise and vibration are often seen as their weakness. For trains running in tunnels where direct airborne noise is effectively screened, structure-borne or 'ground-borne' noise caused by vibration propagated through the ground is the most important concern. The vibration of interest in this case has frequency components from about 15 Hz to 200 Hz.
To understand the mechanisms of vibration propagation from tunnels, a predictive model has been developed for ground vibration generated by a stationary or moving harmonic load applied in a circular lined or unlined tunnel in a layered ground. This study is the first step towards the use of discrete wavenumber methods to model ground vibration from underground trains. Discrete wavenumber methods fall into three categories: the discrete wavenumber fictitious force method, the discrete wavenumber finite element method and the discrete wavenumber boundary element method. This study uses the discrete wavenumber fictitious force method. Based on the moving Green's functions for a layered half-space and those for a cylinder of infinite length, boundary integral equations over the tunnel-soil interface are established. Unlike the conventional boundary integral equation in elastodynamics, the method used here only requires the displacement Green's function. This is achieved by introducing the excavated part of the ground as an extra substructure. The boundary integral equations are further transformed into a set of algebraic equations by expressing each quantity involved in the boundary integral equations in terms of a Fourier series.
Results presented in this paper illustrate the effect of a tunnel on vibration propagation at the ground surface and the difference between a lined tunnel and an unlined tunnel.

A Generic Model for Evaluating the Performance of Base-Isolated Buildings

Summary

Ground-borne vibration has existed ever since the development of urban road and rail networks. Vibration generated by the moving traffic propagates through the ground and into buildings, resulting in unacceptable levels of internal noise and vibration. A common solution to this increasingly significant problem is the base-isolation of buildings by incorporating vibration isolation bearings between the buildings and their foundations. This technique has been employed for over forty years but the exact performance of base isolation remains uncertain.

This paper describes a generic computational model; generic in that it accounts for the essential dynamic behaviour of a typical base-isolated building in order to make predictions of isolation performance. The model is a linear one, formulated in the frequency domain, and consists of a two-dimensional portal-frame model of a building coupled to a three-dimensional boundary-element model of a piled-foundation. Both components of the model achieve computational efficiency by assuming they are infinitely long and using periodic structure theory.

Following an overview of the model, a virtual case study is presented to illustrate its practical application. Along with some initial observations, the case of a point-load surface excitation of the foundation is used to investigate the isolation performance of typical isolation bearings.

Stonely Type flexural waves in thin elastic plates

Summary

The Stonely type waves are known to propagate along free edges of fluid loaded elastic plates. In the case of a plate cut by a straight line two edge waves are possible. One is symmetric and the other is anti-symmetric in the cross section orthogonal to the cut. It is shown that symmetric waves exist at any frequency and for any parameters of the plate and fluid. The anti-symmetric edge wave on the contrary exists only in some frequency range.

In this paper the effects that regulate existence or nonexistence of the anti-symmetric edge wave are analysed and the energy characteristics of edge waves are studied

THE MOVING LOAD ON AN INFINITE CONTINUUM FOUNDATION

Summary

This study proposes a original formalism which permits to analyze the motion of a beam resting on an Winkler infinite continuum foundation and subjected to a moving harmonic load with a constant speed v in the positive x-direction. Such problems present a number of difficulties and most studies have been confined to the case of multispan structures for which the phenomenon of real propagation cannot be taken into account. The method proposed in this study is analytical and takes into account the real phenomena of propagation. The interpretation of this method on the basis of the free-wave propagation equation in periodic structures has led to the definition of the predominant, so-called primary critical speeds. Individual examples were used to test the method. It was also possible to define the limits of a Winkler continuous model in representing the support reactions. In this method is discussed the stability of a dynamic system moving on an infinite periodic foundation. A general method of analysis of such coupled systems is presented. It shows that loads possessing a single point of contact with the foundation become instable at a critical speed highly dependent of the unsprung masses. The evolution of the flutter boundaries as a function of the characteristics of the foundation is described for a typical model

Application of feedback control designto improve the vibrator low frequency distortion

Summary

The power amplifier with vibrator combination of low-frequency primary vibration calibration system at CMS/ITRI has a Total Harmonic Distortion (T.H.D.) of acceleration higher than 2% at less than 2 Hz of its frequency range. To get better calibrated values and to meet the requirements of ISO 16063-11, a wave form comparison feedback control method has been developed to improve the measurement of accelerometer sensitivity.
This paper describes reduction of distortion in motion effect on a low frequency vibration standard, where a laser interferometer is used, with implementation of a feedback loop control software on the calibration scheme. The vibrator signal is measured by an accelerometer located on a moving platform that is driven by the vibrator. The error signal is fed into a controller. Through the multiplication of a factor k and the error signal, the new input signal is obtained of vibrator to reduce the T.H.D. This paper shows the experiment results of 0.8 Hz and 1 Hz. The measured T.H.D. results are both below 2%. In the same time we also evaluate the typed A standard uncertainty for accelerometer voltage sensitivity. The standard uncertainty before and after improvement equals to 0.154% and 0.068%, respectively.

LOW-FREQUENCY TEST CHAMBER WITH LOUDSPEAKER ARRAYS
FOR HUMAN EXPOSURE TO SIMULATED FREE-FIELD CONDITIONS

Summary

The description of a test chamber used for infrasonic and low-frequency experiments, and the theoretical expected characteristics of the produced sound field are presented in this paper. The test chamber has been reconstructed based on an existing infrasound chamber. One of the objectives of this reconstruction has been to increase the frequency range where a flat frequency response can be obtained in a continuous three?dimensional listening region, which occupies a significant part of the volume of the chamber. In addition, the length of the impulse response in this region should be minimised as well. For this purpose, the use of active control has been considered. In the new test chamber, with inner dimensions of 2.72 m x 2.70 m x 2.40 m, a travelling plane wave will be generated; therefore, free-field conditions will be established. The acoustic plane wave will be produced by using a matrix of 4 x 5 loudspeakers in one of the walls. After travelling through the chamber, the sound will be absorbed on the opposite wall, which has a similar matrix of loudspeakers, by using active control. Theoretical results show that it is expected to reproduce recorded signals in free-field conditions within a frequency range of about 2 Hz to approximately 250 Hz. Deviations within ±1.5 dB from a flat frequency response at any point in the listening zone are predicted in this frequency range. In addition, the impulse response will be a good approximation to a delayed delta function in that zone.

ENGINE TEST CELL NOISE EMISSION DESIGN WITH PERFORMANCE VALIDATION RESULTS

Summary

An existing industrial test facility was proposed to be relocated from a plant site in a high ambient noise environment to a community with low ambient noise. The existing facility contained engine test cells and support equipment with loud noise emissions. Residential communities were near the original location, but it was in an industrial park, adjacent to a high-speed multi-lane divided highway. Few noise complaints had been received at the existing location. The proposed future site was in a semi-rural area, alongside a two lane, moderate speed roadway. Although some moderate environmental noise emissions existed from an industrial installation on the existing site, the potential was recognized for community noise disturbance from introduction of a new noise source. JEAcoustics was retained to assess the ambient noise environments and noise emission characteristics for the purpose of determining attenuation requirements for the new facility. A consultant's confidentiality agreement with the owner prevents disclosure of the facility name, plant locations, discussion of plant processes or revelation of other proprietary information. This case study presents the findings of that effort and the noise criteria that were established. Noise control designs and product applications are discussed with results of post-construction noise validation measurements.

LOW FREQUENCY NOISE VERSUS DB(A):DISAPPOINTING EFFECT OF SCREENS ALONG RAILWAYS.

Summary

A series of measurements were carried out to determine the effect of passive noise control screens along a railway. Measurements were done in two cross sections. One was taken over houses and a pnc screen, the other - reference cross section - had no pnc screen.
The screen's height is approximately 4,5 m. The incoming noise was measured at distances of 70 m and 140 m, and at 5 m and 7,5 m above ground level.
Spectral results were available from the 63 Hz octave.

High frequency components were considerably better reduced by the screen than the lower components. The noise spectrum behind the pnc screen shows a strong low frequency character. It clearly showed the typical dual - lightbeam / waterwave - character of noise.
The effect of the screen in the lfn-area is over 5 dB worse than the A-weighed total effect. The dB(A) is not appropiate to predict lfn-effects.
This relative spectral shift (rss) in the noise spectrum can be just as big as the protective effect in dB(A).
The increase of the shift occurs from 4000 to 250 Hz. In this investigation about 10 dB.
The rss becomes less predictable as frequencies are lower and distances larger.
It is necessary to give much more attention to the acoustic effects of doubledecker-trains.

All this requires further research into the course of rss at typical lfn-frequencies. Preferably as a function of kind of trains and distances from source to screen.

THE SOLUTION OF LOW FREQUENCY NOISE PROBLEMS ASSOCIATED WITH A COMBINED HEAT AND POWER PLANT

Summary

Complaints of low frequency noise arose following installation of a CHP system in an existing boiler room. Control was by a multi-stage process, the main phases of which were:

Reduction of LF noise in the boiler room:
Detuning the stack:
Reduction of breakout from the stack:
Identifying the residual problem.

The final phase enabled the correct exhaust silencer to be selected.

The end result was that annoying excitation of room modes and irritating throbbing noises were reduced to below complaint level.

Blasting sound propagation and estimation of psychological and physical effects by blast densification method

Summary

Experimental results on propagation and attenuation of the blasting sounds by underground explosion for preventing liquefaction (Blast Densification Method) are described. The psychological and physical effects by the blasting sounds are estimated by comparison with the previous studies for the effects and evaluation on stationary low frequency sounds and noises. In the field experiments, 127 boreholes were excavated at a flat reclaimed ground of about 4,200 m2, which mainly consisted of sands, and 844 kg of the explosives were charged in the boreholes. The blasting sounds generated by the underground explosions were impulsive low frequency sounds, which predominantly involved frequencies of several Hz. Frequency components above 100 Hz tended to attenuate larger with increasing propagation distance from the blasting area. The sound pressure levels at frequencies above 20 Hz exceeded the hearing threshold level for low frequency sounds of human beings as well as the threshold for rattling of building fittings even at the measuring point about 400 m distant from the blasting area. These results suggest possibility of complaint against the blasting sounds. In order to predict the noise attenuation and estimate the appropriate distance for reducing the possibility of complaint, the results of numerical calculation using the parabolic equation (PE) method under the meteorological conditions are shown.

PROBLEMS OF MEASUREMENT AND EVALUATION OF LOW-FREQUENCY NOISE IN RESIDENTIAL BUILDINGS IN THE LIGHT OF RECOMMENDATIONS AND THE NEW EUROPEAN STANDARDS

Summary

The elaboration covers the methods of measurement of noise from building equipment included in the drafts of the new European standards: pr EN ISO 10052 - survey method and pr EN ISO 16032 - engineering method. The results of acoustic surveys performed in several apartments are the basis for discussing the problems of measurement and evaluation of low-frequency noise, in the light of the binding and the proposed measuring methods.

On the importance of regulating low frequency noise on the "quiet" side of the building.

Summary

This paper describes the first part of an epidemiological study among residents exposed to traffic noise on one side of the building and to low frequency noise from installations on the other side of the building. A questionnaire masked as a general living environment study was delivered to a randomly selected person in each household. In total 41 respondents answered the questionnaire (71% response rate). Noise from installations was measured indoors in a bedroom facing the courtyard in a selection of apartments. 24h traffic noise outdoor and indoor levels were calculated. The noise levels from installations were slightly above or at the Swedish recommendations for low frequency noise indoors with the window closed and exceeded the recommendations by about 10 dB SPL when the window was slightly opened.
The proportion of persons who reported that they were very or extremely annoyed indoors from noise from installations was more than twice as high as for traffic noise. Installation noise also affected respondents' willingness to have their windows open and to sleep with an open window. The high disturbance of installation noises found in this study indicates the importance of also regulating the noise exposure on the "quiet side" of buildings. Further studies will give a better base for the extent of annoyance and acceptable levels of installation noises.

Development of experimental equipment for low frequency sound using a hydraulic servomechanism.

Summary

Experimental equipment was developed to investigate the response of fittings of a house to low frequency sounds. A hydraulic servo system was applied to generate low frequency sounds less than 1 Hz with sound pressure levels of a maximum 150 dB in an airtight box. By doing the feedback of the difference of spectrum between an input signal and an output signal to the input signal, we could regenerate the low frequency sounds whose waveform was almost equal to the input signals. Moreover, we confirmed that this equipment also could be applied to the examination of psychological and physiological effects of low frequency sounds on the human body.

A Noise Control For Continuous Miners

Summary

Over-exposure to noise remains a widespread and serious health hazard in the
U.S. mining and other industries despite 25 years of regulation. Most other categories of illnesses and injuries associated with mining have improved, with the exception of hearing loss. The use of heavy equipment, the drilling of rock, and the confined work environment are just a few factors that contribute to high levels of noise exposure in mining. Simply stated, the majority of miners have a hearing loss by the time they retire. While Noise Induced Hearing Loss is the most common occupational disease in the US, this problem is especially acute among miners.
NIOSH is conducting research to reduce excessive exposure for operators of continuous mining machines and preventing additional cases of Noise Induced Hearing Loss by developing low-cost retrofit of equipment with noise control measures. This paper describes a simple method for reducing the noise from continuous mining machines, which are a major noise source in underground mining. The mine conveyor, used to move coal from the cutting face to the rear of the machine, was identified as the largest noise source and a treatment covering the conveyor flight bars with a durable polyurethane coating was tested as a potential solution. Almost no wear occurred after 90 hrs of continuous use and a 10 dB attenuation was achieved in the octave bands above 2000 Hz

Environmental Assessment of Low frequency noise/Infrasound of Blasting in Japan.

Summary

When a developer develops some area above the definite scale, it is obligated to enforce the environmental assessment. Especially, about the large-scale development of civil engineering such as road highway, river, railroad and power station, the developer must enforce investigation, prediction and assessment in advance to reduce the load on environment.
In case of the development at urban area, blasting with a sort of gunpowder is used. The blast technical method generates easily a big shock noise and an impulsive ground vibration. The low frequency noise and ground vibration occur complainants to the human body and to the wooden houses. This report introduces the real cases, the method of prediction/assessment of low frequency noise and infrasound.