Maximum Permissible Ambient Noise Levels Research Articles

Ambient Noise in Candidate Rooms for User-Operated Audiometry.

Hearing loss is a widespread problem while treatment is not always accessible, mainly because of the limited availability of hearing care professionals and clinics. In this work, part of the User-Operated Audiometry project, we investigate the acoustic environment of inexpensive non-sound-treated rooms that could be used for unsupervised audiometric testing. Measurements of 10 min of ambient noise were taken from 20 non-sound-treated rooms in libraries and private and public clinics, nine of which were measured twice. Ambient noise was compared against two traditional audiometric sound-treated rooms and Maximum Permissible Ambient noise levels by ISO 8231-1, while factoring for the attenuation by the DD450 circumaural headphones provided. In most non-sound-treated rooms, MPAs were violated only by transient sounds, while the floor-noise level was below MPAs. Non-sound-treated rooms' ambient noise levels presented with much larger fluctuations compared to sound-treated rooms. Almost all violations occurred at low to mid-low frequencies. Our results suggest that large-scale implementation of user-operated audiometry outside traditional audiometric rooms is possible, at least under some realizable conditions. Circumaural headphones' attenuation is probably a necessary condition for all cases. Depending on the room, an online system making decisions based on ambient noise might also be included in combination with active attenuation.

Boothless audiometry: Ambient noise considerations

Ambient noise in the test environment will impact signal detection during hearing threshold measurements due to psychoacoustic masking effects. Technical standards specify the maximum permissible ambient noise levels (MPANLs) for use during audiometric testing. MPANLs are dependent on several factors, including transducer characteristics (supra-aural, circumaural, type of ear cushions or earphone enclosures, and insert earphones), the nature of the hearing test being performed (air conduction vs bone conduction and threshold test vs screen at a suprathreshold level), and measurement instrumentation. The nature of the ambient noise (spectrum and constant vs variable) at the test site must be determined and continually accounted for during the boothless hearing test procedure. Ambient noise monitoring procedures are reviewed and examples of ambient noise characteristics in real-world settings, where hearing testing might be performed outside of a sound-treated environment, are provided. Practical considerations are presented, including examples of available tools for ambient noise monitoring, selection of test locations, and transducer attenuation. These are discussed in the context of calculating MPANLs and how best to ensure that ambient noise levels are not negatively impacting the validity of hearing thresholds.

Surveillance for ototoxicity in platinum-based chemotherapy using mobile health audiometry with extended high frequencies.

This study investigated mobile health enabled surveillance in ototoxicity. This was a longitudinal study of 32 participants receiving chemotherapy. Baseline and exit audiograms that included conventional and extended high frequency audiometry were recorded within the patient's treatment venue using a validated mobile health audiometer. Average hearing thresholds at baseline were within the normal range (81.2 per cent left; 93.8 per cent right), reducing at exit testing (71.9 per cent left; 78.1 per cent right). Half of participants presented with a threshold shift according to ototoxicity monitoring criteria. The frequencies affected the most were between 4000 and 16 000 Hz, with left ears significantly more affected than right ears. Noise levels exceeded the maximum permissible ambient noise levels in up to 43.8 per cent of low frequencies (250-1000 Hz). Mobile health supported audiometry proved to be an efficacious tool for ototoxicity monitoring at the treatment venue. Changes in hearing ability over time could be tracked, improving surveillance in patients with full treatment schedules.

Ambient Noise Monitoring during Pure-Tone Audiometry.

There is an increasing need to administer hearing tests outside of sound-attenuating rooms. Maximum permissible ambient noise levels (MPANLs) from published in standards (Occupational Health and Safety Administration [OSHA] 1983; American National Standards Institute [ANSI] S3.1-1999 (R2018)) can be modified to account for the additional attenuation provided by circumaural earphones (relative to supra-aural earphones) that are used for pure-tone audiometry. Ambient noise can influence the results of pure-tone audiometry by elevating thresholds by direct masking and by producing distractions that affect the accuracy of the test. The effects of these distractions have not been studied in relation to pure-tone audiometry in adult listeners. In Part I MPANLs provided by ANSI and OSHA standards are extended to account for the greater attenuation provided by circumaural earphones. Rules ("alerts") were developed taking into account the listeners' thresholds. In Part II effects of distracting noise on pure-tone thresholds are reported. In Part I MPANLs two standards were modified for circumaural earphones by adding the additional attenuation provided by three circumaural earphones (relative to supra-aural earphones). A set of rules ("alerts") is provided for identifying masking effects from ambient noise in a variety of conditions (earphone type, threshold elevation, uncovered ear). In Part II the distracting effects of an industrial noise sample on thresholds obtained from five listeners with normal hearing are described. Pure-tone thresholds were measured in quiet and in distracting noise presented at various levels. The effects of the distracting noise on the following variables were measured: time per trial, number of trials required to measure threshold, threshold shift, and perceived distractibility of the noise. Time per trial was unaffected by distracting noise. Number of trials required for threshold, threshold shift, and perceived distractibility increased with distracting noise level. Part I: The modified MPANLs provide more relevant determinations of the potential effects of ambient noise on pure-tone thresholds than the values in the standards. Part II: Distracting noise affects pure-tone threshold measurements in a manner that is different from direct masking. The potential contaminating effect of distracting noise can be measured and reported.

An evaluation of the Sennheiser HDA 280-CL circumaural headphone for use in audiometric testing

Objective: Evaluation of the Sennheiser HDA 280-CL circumaural headphone for the determination of (1) equivalent threshold sound pressure levels (ETSPL) for 125–18,000 Hz.; (2) real ear attenuation (250–8000 Hz); (3) insertion loss (63–18,000 Hz); (4) frequency response (125–18,000 Hz); (5) total harmonic distortion (THD) (125–10,000 Hz); and, (6) linearity (11,200–18,000 Hz).Study Sample: Twenty-five normal hearing adults aged 18–25 participated in (1) and (2).Design: (1) Hearing thresholds were measured using the Sennheiser HDA 280-CL. Frequency specific ETSPL values were calculated in an artificial ear. (2) Sound field thresholds were measured with the ears open and covered with the headphone to obtain the real ear attenuation thresholds (REAT). These values were used to determine the maximum permissible ambient noise levels (MPANL). (3) A B&K HATS mannequin recorded the output levels of a broadband pink noise with the ears open and covered with the headphones. (4, 5) The frequency response, THD and linearity were measured in an artificial ear.Results: Values for ETSPL, REAT, MPANL, insertion loss, as well as measures of frequency response, THD and linearity are presented.Conclusions: The Sennheiser HDA 280-CL meets the requirements for audiometric testing and the values presented can be used for calibration.

Out-of-Booth Testing with Noise-canceling Earphones

Out-of-Booth Testing with Noise-canceling Earphones

Affordable headphones for accessible screening audiometry: An evaluation of the Sennheiser HD202 II supra-aural headphone

Objective: Evaluation of the Sennheiser HD 202 II supra-aural headphones as an alternative headphone to enable more affordable hearing screening. Design: Study 1 measured the equivalent threshold sound pressure levels (ETSPL) of the Sennheiser HD 202 II. Study 2 evaluated the attenuation of the headphones. Study 3 determined headphone characteristics by analyzing the total harmonic distortion (THD), frequency response and force of the headband. Study sample: Twenty-five participants were included in study 1 and 15 in study 2 with ages ranging between 18 and 25. No participants were involved in study 3. Results: The Sennheiser HD 202 II ETSPLs (250–16000 Hz) showed no significant effects on ETSPL for ear laterality, gender or age. Attenuation was not significantly different (p > 0.01) to TDH 39 except at 8000 Hz (p < 0.01). Maximum permissible ambient noise levels (MPANL) were specified accordingly. The force of the headband was 3.1N. THD measurements showed that between 500 and 8000 Hz intensities of 90 dB HL and higher can be reached without THD >3%. Conclusion: Sennheiser HD 202 II supra-aural headphones can be used as an affordable headphone for screening audiometry provided reported MPANLs, maximum intensities and ETSPL values are employed.

The Acoustic Test Environment for Hearing Testing.

Audiology clinics traditionally employ expensive, prefabricated sound rooms to create an environment that is sufficiently quiet for accurate hearing tests. There is seldom any analysis of the need for or benefit from such enclosures. There may be less expensive methods that would decrease the cost of and increase access to hearing testing. This report provides information concerning the need for and effectiveness of sound rooms and an analysis of the audiometric test ranges for various earphone/room combinations. Acoustic measurements made in four rooms were analyzed with the attenuation provided by various earphone designs to determine the maximum permissible ambient noise levels and the corresponding audiometric test ranges. The measurements and calculations were performed with four test rooms and five earphone designs. Ambient noise levels and earphone attenuation characteristics were used to calculate the noise levels that reach the ear. Those were compared to the maximum permissible ambient noise levels that are provided in ANSI S3.1-1999 or calculated from measured attenuation levels. These measurements were used to calculate testable ranges for each room/earphone combination. The various room/earphone combinations resulted in minimum test levels that ranged from -10 to 20 dB HL at various test frequencies. When the actual benefits of expensive prefabricated sound rooms are assessed based on the range of hearing levels that can be tested, the effectiveness of that approach becomes highly questionable. Less expensive methods based on planning the clinic space, use of inexpensive sound treatments, and selecting an appropriate earphone can be effective in almost any space that would be used for hearing testing.

Pure-tone audiometric threshold assessment with in-ear monitoring of noise levels

Objective: Our objective was to obtain reliable threshold measurements without a sound booth by using a passive noise-attenuating hearing protector combined with in-ear 1/3-octave band noise measurements to verify the ear canal was suitably quiet. Design: We deployed laptop-based hearing testing systems to Tanzania as part of a study of HIV infection and hearing. An in-ear probe containing a microphone was used under the hearing protector for both the in-ear noise measurements and threshold audiometry. The 1/3-octave band noise spectrum from the microphone was displayed on the operator's screen with acceptable levels in grey and unacceptable levels in red. Operators attempted to make all bars grey, but focused on achieving grey bars at 2000 Hz and above. Study sample: 624 adults and 197 children provided 3381 in-ear octave band measurements. Repeated measurements from 144 individuals who returned for testing on three separate occasions were also analysed. Results: In-ear noise levels exceeded the maximum permissible ambient noise levels (MPANL) for ears not covered, but not the dB SPL levels corresponding to 0 dB HL between 2000–4000 Hz. In-ear noise measurements were repeatable over time. Conclusions: Reliable audiometry can be performed using a passive noise-attenuating hearing protector and in-ear noise measurements.

Advances in Hearing Conservation Practices: An Interview With Mark Stephenson

Abstract It is estimated that 30 million Americans are exposed to hazardous noise levels at work (Stephenson et al., 2003). The Occupational Safety and Health Act of 1970 created two separate agencies dedicated to promoting worker health and safety: the Occupational Safety and Health Administration (OSHA) and the National Institute for Occupational Safety and Health (NIOSH). Research at NIOSH informs OSHA regulations. This report comprises an interview with Mark Stephenson, PhD, Scientific Research Coordinator for the NIOSH noise and hearing loss research program. He provides insights into the latest advances in hearing conservation practices, what works and why. Current hearing conservation practices developed at NIOSH and not yet mandated by OSHA use methods borrowed from evidence-based health communication theories to change the ways individuals view the problem of noise exposure, eliminate barriers that prevent effective hearing protector use, and create a culture of self-efficacy with respect to hear...

ANSI update: maximum permissible ambient noise levels for audiometric test rooms.

The American National Standards Institute (ANSI) specifies maximum permissible ambient noise levels (MPANLs) allowed in an audiometric test room to ensure that hearing thresholds obtained down to 0-dB HL will not be elevated due to masking by ambient noise. MPANLs were originally specified in 1960 and have been revised in 1977, 1991, and most recently in 1999. The purpose of this report is to offer an overview by providing a historical perspective of the MPANLs recently specified by ANSI (ANSI S3.1--1999), the rationale for revising the MPANLs, the new computational method used for determining the 1999 MPANLs, the ANSI S3.1--1999 octave and one-third octave band MPANLs, and information concerning compliance with the new MPANLs.

Ambient noise levels in nursing homes: implications for audiometric assessment.

Conducting hearing tests and hearing screenings in the nursing home environment can be a challenge. One issue which may affect the validity of the test results is the level of ambient noise in those facilities when a sound-treated booth is not available. This study sampled the ambient noise levels in ten different nursing homes and compared those results to the ANSI S3.1--1999 criteria for maximum permissible ambient noise levels. Based on the results of this investigation, the use of insert earphones for air conduction assessments is recommended when a sound-treated booth is unavailable and noise levels exceed the ANSI criteria. Other suggestions regarding air-conduction and bone-conduction assessments are discussed.

Ambient Noise Levels in Mobile Audiometric Testing Facilities: Compliance with Industry Standards

Excessive ambient noise levels in audiometric test booths may elevate and therefore invalidate hearing thresholds of employees included in a hearing conservation program. This study was conducted to determine if a sample of mobile test vans and trailers operating in the Midwest met the 1983 Occupational Safety and Health Administration (OSHA) maximum permissible ambient noise levels (MPANLs), the MPANLs in the American National Standards Institute (ANSI) S3.1-1991, and the suggested National Hearing Conservation Association (NHCA) values. Ambient noise levels were measured in 13 audiometric test booths contained in 12 different industrial mobile test vans and trailers operating in the Midwest. Results indicated that all 13 (100%) of the industrial mobile test vans and trailers evaluated complied with 1983 OSHA permissible levels and the NHCA 1996 recommended levels. With regard to the 1991 ANSI MPANLs, 5 (38%) of the 13 booths were in compliance at all frequencies. Those that failed did so at 125, 250, and 500 Hz. It appears that the NHCA levels need to be used for all hearing conservation programs with respect to compliance for noise levels in mobile audiometric test booths.

The maximum permissible ambient noise and frequency-specific averaging time on the measurement of distortion product otoacoustic emissions.

The effects of ambient noise and averaging time on distortion product otoacoustic emission (DPOAE) measurements were systematically examined in 20 normally hearing adults. For each frequency from 0.7 to 6 kHz, 2f1-f2 DPOAEs were measured at nine intensity levels of ambient noise for each of four different averaging times. The dependent variable of interest was the DPOAE:noise ratio (D:N)--the relationship between DPOAE amplitude and noise level at 2f1-f2. Findings indicated that, relative to the baseline condition (25 dBA), ambient noise levels of 40 dBA or greater affected the D:N considerably in the lower frequencies. However, noise levels of 55-65 dBA did not affect the D:N in the higher frequencies. Results also indicated that, to achieve detectable DPOAEs, longer averaging times were required as ambient noise increased and as frequency decreased. Based on the results, the maximum permissible ambient noise levels (MPANLs) were estimated in relation to averaging time.

Effect of audiometric test room noise on monaural and binaural thresholds

This study determined if the maximum permissible ambient noise levels (MPANLs) for audiometry specified in the revision of ANSI S3.1-199x provided the same amount of threshold shift for monaural and binaural listening. Sound-field monaural and binaural warble-tone thresholds (125–8000 Hz) were obtained on 24 normal-hearing subjects in quiet (ambient) and in two background noise conditions. One noise condition approximated the ANSI S3.1-199x ears not covered MPANLs (ANSI noise). The other noise condition was 20 dB higher than the ANSI MPANLs (ANSI noise + 20). Monaural thresholds were about 2 dB higher than binaural thresholds in quiet and in each noise condition. The difference between the monaural minus the binaural threshold shifts in each noise condition (ANSI noise + 20 minus ambient; ANSI noise minus ambient) averaged over frequency was typically less than 1 dB. Thus the MPANLs in the revision of ANSI S3.1-199x are appropriate for both monaural and binaural testing.

Ambient Noise Levels in Industrial Audiometric Test Rooms

In 1983 the Occupational Safety and Health Administration (OSHA) specified maximum permissible ambient noise levels (MPANLs) that would allow valid hearing threshold measurements in an audiometric test room. However, ambient noise sound pressure levels (SPLs) in rooms used for industrial hearing tests are unknown. The present study reports octave band (125 to 8000 Hz) ambient noise SPLs measured in 490 single-walled prefabricated audiometric test rooms located in industrial settings that were obtained from eight sources. The ambient noise SPLs were highest in the lower frequencies and decreased as frequency increased. All 490 rooms met the OSHA MPANLs. Fortunately, the ambient noise SPLs were considerably lower than the OSHA MPANLs, since previous research has demonstrated that hearing thresholds cannot be obtained down to 0-dB HL in a test room having ambient noise levels equal to the OSHA MPANLs. In fact, 33%, or 162 of the 490 test rooms, met the more stringent MPANLs recently specified by the American National Standards Institute (ANSI) for industrial hearing testing. Given that the OSHA MPANLs are too high and that the test room ambient noise SPLs were considerably less than the OSHA MPANLs, that authors recommend that the OSHA MPANLs be revised to the more stringent ANSI 1991 MPANLs so that hearing thresholds for baseline and annual audiograms can be measured down to 0-dB HL.

Ambient noise levels in audiometric test rooms used for clinical audiometry.

Recently, the American National Standards Institute (ANSI) has specified (ANSI S3.1-1991) maximum permissible ambient noise levels (MPANLs) allowed in an audiometric test room that would produce negligible masking of pure tones presented down to O-dB HL for two test conditions (ears covered, ears not covered) and three test frequency ranges (125-8000 Hz, 250-8000 Hz, 500-8000 Hz). In the present study, octave band ambient noise sound pressure levels were measured in 136 audiometric test rooms used for clinical audiometry and compared with the ANSI octave band MPANLs for each test condition and frequency range. For the ears covered condition, about 50% of the rooms were in compliance (passed) with the MPANLs for the 125-8000 Hz and 250-8000 Hz range and 82% for the 500-8000 Hz range. For the ears not covered condition, only about 14% of the rooms passed for the 125-8000 Hz and 250-8000 Hz range and 37% passed for the 500-8000 Hz range. The primary cause of the low pass rate for each test condition and frequency range was attributed to low frequency (125-500 Hz) ambient noise presumably from the ventilation system.

Ambient noise levels in audiometric test rooms

Octave-band ambient noise levels measured in 136 diagnostic and 202 industrial audiometric test rooms were compared with the maximum permissible ambient noise levels (MPANLs) specified in ANSI S3.1-1991. The mean octave-band ambient noise levels for the diagnostic rooms were less than the ears covered but higher than the ears not covered MPANLs for each test frequency range specified in ANSI S3.1-1991. Specifically, 68 (50%), 69 (51%), and 112 (82%) of the diagnostic rooms met the ANSI ears covered MPANLs for the 125- to 8000-Hz, 500- to 8000-Hz test frequency ranges, respectively; however, only 14 (11%) for the 125- to 8000-Hz and 250- to 8000-Hz test frequency ranges and 39 (29%) for the 500- to 8000-Hz test range met the ANSI ears not covered MPANLs. The mean octave-band noise levels for industrial rooms were lower than the ANSI ears covered MPANLs for the 500- to 8000-Hz test frequency range except at 250 and 500 Hz where the levels exceeded the ANSI MPANLs by 2.4 and 6.4 dB, respectively. For the industrial rooms, 66 (33%) met the ANSI ears covered MPANLs for the 500- to 8000-Hz test range. Overall, both the diagnostic and industrial test rooms most often failed to meet the ANSI MPANLs at 250 and 500 Hz. Implications for diagnostic and industrial hearing testing will be discussed.

Effects of ambient noise masking on earphone thresholds.

Monaural thresholds were measured for 24 normally hearing subjects using TDH-49P, Audiocup, and ER-3A earphones from 500 to 6000 Hz in quiet and in background noise having maximum permissible ambient noise levels (MPANLs) specified by OSHA (1983) and ANSI (S3.1-1991). The attenuation for each earphone system was obtained and the actual threshold shift was compared to the predicted threshold shift. The mean threshold shifts were negligible (≤2 dB) in the ANSI MPANLs regardless of earphone and in OSHA MPANLs for the ER-3A but ranged from 2 to 7.5 dB for the Audiocup and from 6 to 12.5 dB for the TDH-49P in the OSHA MPANLs. The results of this study suggest that OSHA MPANLs are too high to allow for testing down to 0-dB HL using these earphones. The high noise-reducing properties of the ER-3A would make it the earphone of choice if testing is done in OSHA MPANLs. Testing down to 0 dB HL can be done in the newly specified ANSI MPANLs regardless of earphone type.