ANSI S12 Research Articles

Evaluation of ANSI low frequency measurement standard S12.9 part 7 in light of current research

ANSI S12.9 Part 7 (2016) Measurement of Low-frequency Noise and Infrasound Outdoors in the Presence of Wind and Indoors in Occupied Spaces was developed over 2-3 years and was a much needed guide to standardize the measurement of low frequency sound and infrasound. Since then, research has advanced what are now considered best practices, and technology has advanced to make instrumentation available to consultants and researchers to help solve several limiting issues in measurements. This paper provides a review of the standard and recommends improvements to the techniques used in the measurement of low frequency-infrasound outdoors. These improvements include better assessment and understanding of wind noise, the importance of sensor placement, and advances in transducers, wind screening, arrays and calibration. The information provided includes best practice with a conceptual understanding of the interaction with the environment in low frequency-infrasound measurement; references are provided for a deeper dive into each topic.

ECMA-418-2 roughness, a challenging implementation

Over the past decade, psychoacoustics has grown significantly and sound quality metrics have become an easy way to include the human factor in NVH analysis. Most of these metrics have been defined by standards (ISO, DIN, ANSI or ECMA), which should promote their use in industrial applications. MOSQITO is an open-source project providing implementations of sound quality metrics in Python(e.g. loudness ISO 532-1, sharpness DIN 45692, SII ANSI S3.5) along with complete documentations and validation procedures. In 2020, the European Computer Manufacturers Association released the ECMA-418-2 standard, revised in 2022, describing new loudness, roughness and tonality implementations based on a common hearing model. During the implementation of the roughness metric in MOSQITO, it appeared that some implementation instructions are subject to interpretation, and some information was missing in the standard to allow for a valid computation of this metric. Moreover, the standard does not define some validation cases, which can limit the spread of its metrics. This paper highlights these difficulties for each section of the calculation process, and proposes new steps that would aid the user's understanding and implementation of the standard.

Forecasting community response to low-frequency noise

The most common approach to managing environmental noise is by reference to A-weighted sound levels deemed appropriate for the community. These criteria are usually derived from transportation noise studies for which the relative proportion of low-frequency noise is implicit. Very different community reactions can arise when source spectra don't represent those studied. Responses diverge even further when the listeners' context also differs from that originally studied. This is nowhere more evident than in the case of large industrial equipment (such as power plants and gas compressor stations) sited in rural areas, due in large part to strong Low-Frequency Noise (LFN). Guidance for forecasting community reaction to LFN is scattered throughout the literature as individual studies employing a diverse assortment of approaches and noise descriptors. The purpose of the present paper is to demonstrate a straightforward, comprehensive, and unified forecasting approach suitable for inclusion in ANSI S12.9 Part 4 "Noise Assessment and Prediction of Long-Term Community Response", similar in many respects to the method recently deleted from this standard (2005 Annex D).

Categorization of pickleball paddles as a highly impulsive sound source

As the sport of pickleball has grown in popularity and tennis courts close to homes are being converted to this use, noise regulation for pickleball courts has become a topic of discussion among city councils, planners, home owners associations, residents, and, increasingly, attorneys seeking injunctions against poorly sited or mitigated courts. Accurate noise impact assessment of the short duration impulsive sound produced by the impact of the ball on the paddles requires the use of the highly impulsive adjustment in ANSI S12.9 Part 4. Examination of the definitions of impulsive sound in this standard and in ISO 1996 Part 1 identifies characteristics of rapid onset, significant energy in the most sensitive part of the auditory spectrum, and duration as primary differentiators for categorization. The noise impact assessment methodology in ANSI S12.9 Part 4 for highly impulsive sound has proven an effective means of determining the amount of mitigation needed for pickleball facilities, being more repeatable and precise than other commonly used assessment methods while avoiding underestimation of annoyance.

Effect of shooting glasses on earmuff attenuation measured with an acoustic test fixture for gunfire impulses

The EPA requirement for hearing protector labels is based on the decrepit ANSI S3.19-1974 standard, which prohibits the use of eyewear during the REAT testing that leads to the NRR on the product label. Firearm users are recommended to wear protective eyewear while shooting. In this presentation, we review past work regarding the effects of eyewear on earmuff performance and present results from five samples of one product that includes both eyewear and an earmuff. Impulses ranging between 139 and 178 dB peak SPL were used. Impulse Insertion Loss was less than 10 dB below 400 Hz for earmuffs alone and negligible for the earmuff and glasses condition and attenuation in the high frequencies was reduced by approximately 15 to 25 dB. Impulse peak insertion loss values per ANSI S12.42 were reduced from 21 to 39 dB for the earmuff alone to 15 to 22 dB when eye protection was added. Hearing conservation programs need to account for the deleterious effect of protective eyewear on earmuffs, and additional studies with broad combinations of earmuffs and eyewear are needed to establish the range over which eyewear can be expected to compromise earmuff attenuation.

Comparison of reverberation times and average absorption coefficients in classrooms, based on in situ measurements versus calculated from material databases as during design

Reverberation time (RT) is an acoustic descriptor used widely by acousticians for characterizing indoor acoustic environments, as specified in standards such as ANSI S12.60 “Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools”. It is often calculated in the design phase for simple spaces by applying equations like Sabine’s or Eyring’s, requiring information on room dimensions and the surface areas and acoustic absorption coefficients across frequency of room materials. In this project, measured RTs from a recent survey of over 200 K-12 classrooms are compared against the RTs predicted across speech frequency octave bands using Sabine’s and Eyring’s equations. Agreement between predicted and measured values varies based on the octave band and material selection. The working group currently revising ANSI S12.60 is considering providing guidance on the desired average absorption coefficient in classrooms, rather than reverberation time, so this study also compares the average absorption coefficients for the classrooms. The coefficients are back-calculated from the measured RTs using Sabine’s and Eyring’s equations, and compared against those calculated from surface dimensions and commonly available material absorption coefficients.

Measuring hearing protector attenuation of impulse noise on acoustic test fixtures using maximum A-weighted energy reduction

Hearing protection devices (HPDs) and firearm suppressors can help mitigate risk of hearing loss from small caliber firearms. ANSI S12.42 is the standard for measuring HPD impulse peak insertion loss (IPIL). No consensus standard exists for measuring firearm suppressor noise reduction, though the industry is working toward a standard using maximum accumulated A-weighted energy. A common attenuation metric for different impulse noise reduction technologies would inform the individual and combined impact of these technologies. The maximum A-weighted energy reduction for several HPDs was assessed using firearm impulses from two rifles (0.300 Winchester Magnum and 5.56x45) with two ATFs and five field microphones positioned on opposite sides of the gun at four locations (field levels between 180- and 140-dB pSPL). No adjustments were made to account for tissue/bone conduction. Maximum A-weighted energy reduction values for single protection ranged between 17 dB (earmuff with safety glasses) and 43 dB (preformed earplug). Similar to IPIL, maximum A-weighted energy reduction increased with increased impulse levels. Advantages, disadvantages, and technical issues associated with the procedure will be discussed.

Protecting beyond the bone-conduction limit: Lessons learned developing and fielding a passive Hearing Protection Helmet

Traditional hearing protection devices focus on attenuating air-conducted sound and are limited by the bone conduction threshold (Berger, 1983). In extreme noise fields, such as aircraft maintainers operating near jet engines on aircraft carriers, the bone conducted pathway carries sufficient energy to damage the cochlea. Here, we describe the development, qualification, and field-testing of a passive Hearing Protection Helmet (HPH) designed to surpass the bone conduction limit. The HPH features a noise-isolating shell sealed to the head via a compliant edge seal. When worn with foam earplugs and tested to ANSI S12.6-2016 (Experimenter Fit), the Noise Reduction Rating (NRR) of the HPH is 38 dB and the Noise Reduction Statistic (NRSA) (ANSI S12.68) (80% to 20% of users) is 45 to 52 dB. We also describe challenges associated with user acceptance of the HPH. User feedback led to the integration of an electronic hear-through system to restore auditory situational awareness. Users also rejected wired communication-enabled ear plugs, resulting in the integration of ear cup speakers and adding challenges associated with setting the hear-through sound pressure level limits. We conclude with anecdotes from trial deployments aboard U.S. Navy Aircraft Carriers in 2020, 2022, and 2023.

Benefits of using ANSI/ASA S12.9 -2020/Part 7: “Measurement of environmental sound: Measurement of low-frequency noise and infrasound outdoors and in the presence of wind and indoors in occupied spaces.”

I was invited and honored by Dr. Paul Schomer to Chair working group S12/WG 54 for Part 7 of ANSI S12.9. The working group had 23 learned members all at the reasonable disposal of the Chair. At the start I knew the technical tasks that would have to be done and it would be a time-consuming process, at least a year; completion took over three years. Some of the fundamental tasks required were (a) Define and quantify wind-induced-noise (WIN) for standard wind screen measurements and with upgraded wind protection to lower WIN, (b) Define conversion corrections necessary between post-mounted above grade and ground plane mounted microphones, and (c) Define a repeatable technique for measuring pressure levels outside and inside structures to characterize noise reduction NR in 1/3 octave bands for the facade of the structure. These tasks were completed with much effort by numerous group members. The standard may be consulted for analyses and reference, particularly Annexes A through D, as well as for authoritarian standard purposes. This presentation will outline the many valuable procedures in the standard for measuring low frequency noise and infrasound.

Background Sound Levels in Rural Areas of the U.S.

ANSI S12.9 Part 3 Annex C provides a compilation of the average daytime, nighttime, and day-night sound levels in six land use categories, ranging from Category 1 - "very noisy urban residential" to Category 6 - "very quiet suburban and rural residential." However, the data in table C.1 of the standard, which provides typical day, night, and day-night sound levels by land use category, is based primarily on more urbanized areas, and provides caution in using the data for the less densely developed land use Categories 5 and 6. In this paper we supplement this Annex by providing a collection of ambient sound level data at over 150 rural locations primarily in the northeastern and midwestern U.S. As the ambient sound level is not a single metric, the results include the range of sound levels in various metrics, including the A-weighted L10, L50, L90, and Leq, for the daytime and nighttime, and DNL. Unweighted octave and 1/3 octave band ranges and averages are also presented for each metric. Where possible, we also compare these results at individual locations to the predictions made by national noise mapping programs.

Comparison of three calibration procedures for free-field reference speech audiometry

Objective In standards IEC 60645-1 and ANSI S3.6, the free-field equivalent earphone output level method is assumed as the reference for speech audiometry. Three calibration procedures for this method were compared in this study. Design Speech audiometry was conducted with Dutch consonant-vowel-consonant words for the following conditions: 1. TDH39 earphones, 2. loudspeaker, and 3. free-field simulated with TDH39 earphones. The first calibration procedure was based on the empirically determined difference between the speech recognition threshold (SRT) with earphones and a loudspeaker. The second procedure was based on the theoretical free-field correction, derived from the known speech spectrum and the free-field to coupler difference. The third calibration procedure corresponded to the results of the free-field simulated speech material under earphones. Study sample The sample included 20 normal hearing subjects. Results The differences between the observed SRT in the free-field and earphone conditions and the free-field and simulated free-field conditions were 7.1 dB and 0.6 dB, respectively. Conclusion The three calibration procedures for the free-field equivalent output method yielded approximately the same results, and therefore all appear to be useful for TDH39 earphones.

In-Progress Updates to ANSI S12.60 Part 1 Pertaining to Building Sound Isolation

In early 2022, work began to update ANSI/ASA S12.60, Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools—Part 1 Permanent Schools. The current version of this standard is from 2010. When the working group was polled for comments and requested changes for a new version of the standard, concerns regarding how the 2010 version handles building envelope sound isolation requirements were numerous. The current progress of the working group’s actions regarding modifications to the standard’s building envelope sound isolation language will be discussed.

Relationships between Acoustics, Thermal, Indoor Air Quality, and Lighting Conditions on Student Achievement in K-12 Classrooms

Data on acoustic, thermal, indoor air quality, and lighting conditions have been collected from 220 classrooms in the midwestern United States. Gathered acoustic data include sound levels logged every 10 seconds and room impulse responses from which reverberation times were extrapolated. K-means clustering was used to group the logged sound data into times when speech was or was not occurring; then acoustic metrics were calculated from the clustered data. When comparing the measured acoustic conditions to ANSI S12.60, 91% of the classrooms did not meet the recommended maximum background noise level for unoccupied conditions, while 15% did not meet the recommended maximum reverberation time. The field measurements also revealed that only 20% of the classrooms met ASHRAE Standard 62.1 ventilation rate requirements, while all classrooms met recommended IES illuminance level for reading and writing. Multivariate linear regression analyses between the environmental conditions and student achievement data, while controlling for student demographics, have identified a number of significant relationships. This presentation summarizes key results, describes how acoustic conditions were correlated to building mechanical systems, and considers how indoor environmental quality may be optimized to benefit occupants in educational settings. [Work supported by the United States Environmental Protection Agency Grant Number R835633.]

인공 유양돌기를 이용한 이식형 골전도 보청기용 진동체 성능 평가

This study describes the driving principle and design of the bone conduction transducer that has improved the problems of the previously bone conduction transducer, and by evaluates the performance using the artificial mastoid. Through finite element analysis, the Lorentz force of the transducer was calculated and the shape of the vibrational membrane suitable for conductive hearing loss was derived. Compared to the previous transducer, the improved transducer has increased vibration displacement by about 6dB in all frequency bands. Based on the analysis results, a bone conduction transducer was implemented, and the output force level and total harmonic distortion were measured using an artificial mastoid. The output force level of the transducer was evaluated by comparing it with the output force level of the conventional bone conduction implant (BoneBridge). In addition, total harmonic distortion was evaluated based on ANSI S3.6 regulations. The improved transducer is judged to have a sufficient function as a transducer for bone conduction implants in the 1∼3kHz band which is the most important for speech discrimination. However, the output force level and total harmonic distortion in the low frequency band (less than 1 kHz) need improvement studies.

Revision of ANSI S12.7 methods for measurements of Impulse Noise

ANSI S12.7 Methods For Measurements Of Impulse Noise 1986 (R2006) applies to all kinds of impulsive noise, whether discrete event sources, such as quarry and mining explosions or sonic booms, or from multiple event sources such as pile drivers, riveting, nail guns, or rifle or gun firing. The working has been working on proposed changes to the measurement methods, especially high speed digital waveform recording techniques to improve the accuracy of capturing the peak of the waveform as well as the details of the structure. The presentation will describe the proposed changes to the measurement methods and measurement microphones as well as the applications of the revised standard once it is approved.

Design and implementation of a signal processing ASIC for digital hearing aids

People with hearing loss can be benefited from assistive devices like hearing aids. This article presents the implementation of a signal processing chip for digital hearing aid applications. The functionality of the proposed design was tested in real-time using two field programmable gate arrays (FPGAs), one of them modeled as a hearing aid processor and the other as an external audio CODEC. The hearing aid processor contains an 18-band 1/3-octave ANSI S1.11 filter bank, which performs the audiogram compensation and a dynamic range compression algorithm to restrict the output signal to an acceptable loudness. The functionality of an external audio CODEC was replicated in the other FPGA to act as the analog front end circuit of a hearing aid. Serial Peripheral Interface (SPI) was used for communication between the two FPGAs. The SPI protocol was modified to make the hearing aid programmable through the data in line of the interface itself. The proposed hearing aid chip was implemented using standard cell based design flow with a 5x5 mm fixed die size intended to fit in a 48-pin package.

Advancing support for cause-and-effect models by estimating the kurtosis statistic using fractional-octave-band filters

This paper presents a preliminary method for estimating signal processing parameters that optimally satisfies accuracy and resolution requirements for the sound pressure level and kurtosis level. The kurtosis statistic has long been studied and more recently used for applications in acoustics and vibrations such as architectural acoustics, hearing loss, noise exposure, and accelerated material and structural life testing. The temporal and spectral characteristics of many quantities are evident by time-frequency analysis including hearing, finger sensation, sound diffusion, and reverberation. Some research has conditioned on frequency content while other research has not. Simpson's reversal may potentially adversely affect the models if frequency content is not considered. Modeling techniques which relate cause-and-effect are more likely to result in successful models. Models of human hearing are particularly sensitive to the frequency content because the tonotopic organization of the cochlea induces a cause-and-effect relationship from sound incident on the ear to the basilar membrane. The fractional-octave-band filters specified in ANSI S1.11 and IEC 61260-1 are well developed for conditioning on frequency bands. This paper provides details of the process for optimizing the filter parameters. Additional optimization and testing is described for developing a faster and more accurate method with better support for causal inference.

Conforto Acústico: um caminho possível para a Saúde dos Profissionais a exercer em escolas

Introduction Tree planting reduces noise pollution and consequently improve the quality of life, however, in Brazil there is little research on this topic, mainly related to the quantification and classification of vegetation in the health of workers. It is understood that the correct planning of afforestation at school is essential, as it makes the place attractive, with functional and aesthetic quality, adequate landscaping and favorable acoustic conditions. Thus, acoustic comfort can favor the teaching process, as it minimizes the educator's vocal effort. Given these considerations, this work exposes the need to obtain acoustic comfort in a school located in the central area of a city in the interior of the State of São Paulo, Brazil. Objective To measure the sound pressure levels in three environments in the school yard of a central school in a city in the interior of the state of São Paulo, Brazil; verify the existence of arboreal masses in the school yard and near the school under study and to find out if the tree mass contributes to the acoustic comfort of the school yard under study. Methodology The measurement of sound pressure levels was carried out in the school yard in October 2019, at 9:30 am within the three established points. The measurement followed ANSI S12.60 recommendations, using Instrutherm DEC-5050 sound meter equipment and compared with NBR 10.151 and NBR 10.152 Standards. At the three determined points, 30 measurements were performed at each point, spaced 10 seconds each, at each point, according to the manual for measurement and calculation of acoustic conditions. Measurements were taken at 1.2 m above ground and 1.5 m from walls. Results The school does not comply with NBR 10152, with sound pressure levels up to 88.9 dB (A), with regard to acoustic comfort, compromising the occupational health and quality of life of educators and the learning process of students. The lack of arboreal mass can significantly contribute to noise pollution and compensatory considerations of mitigating proposals in future studies to solve the acoustic problems that affect the lives of educators and students. Conclusion Environmental noise in the school yard is above acceptable limits, impacting acoustic quality and comfort, which can contribute to a process of auditory effort, which impairs the teaching process and quality of life, interfering with the health of educators and students. Therefore, it is essential to search for solutions to improve the acoustic quality of the environment, with a favorable acoustic landscape. The arboreal mass shows promise for acoustic comfort in the school environment, providing better health conditions for educators and students. Therefore, it is suggested as future studies: Propose the type of material for the architectural space so that the place has less noise; improve the positioning of the afforestation present at the site and Implement afforestation project as needed by the site. Keywords: Acoustic comfort, Trees, Schoolyard, School Health Program, Occupational Health.

Amplification rationale for hearing aids based on characteristics of the Japanese language

ObjectiveHearing aid amplification rationales have typically been developed by using global averages of the long-term average speech spectrum (LTASS) from Western European languages. However, there are few reports on hearing-aid amplification based on acoustic-phonetic characteristics of the Japanese language. This study’s objective is to investigate the LTASS for Japanese, and to compare a typical amplification rationale originally developed mainly for Western European languages with an amplification rationale specifically adjusted to the LTASS for Japanese. MethodsLTASS for two speech materials provided by four Japanese talkers were analyzed using 1/3 octave bandwidth filters. The speech was recorded with different levels of vocal effort, yielding three LTASS for “soft”, “moderate” and “loud” speech. From these results, a gain offset of the hearing-aid amplification for Japanese was obtained as compared to ANSI S3.5. Speech intelligibility for an amplification rationale for Western European languages and the newly-developed Japanese version was obtained for presentation levels of 50 dB SPL, 65 dB SPL and 80 dB SPL. Nineteen people with mild to moderate hearing loss participated in the speech intelligibility experiment. Scores in% correct were arcsine-transformed and subjected to repeated measures ANOVA with pairwise comparisons of significant main effects using Bonferroni adjustments for multiple comparisons. ResultsThe LTASS for Japanese was slightly different from the values of previous reports. A comparison of LTASS values to ANSI S3.5 with values for Japanese showed that the Japanese amplification rationale for “moderate” speech levels required more gain in the low-frequency area, and less gain in the high-frequency area. There was no significant difference in the speech intelligibility level between the amplification characteristics of Western European languages and Japanese language at each presentation level. ConclusionIt was shown that for hearing-aid amplification for Japanese, adjustments based on LTASS differences for Western European Languages could be made. This preserved speech intelligibility at the same level as the original amplification rationale, suggesting that there was no need to consider differences in phonetics of Japanese to optimize speech understanding.

The reinstatement of Working Group 41 (ANSI S12.66) guidelines for developing a community noise ordinance or regulation: First steps

The reinstatement of Working Group 41 (ANSI S12.66) guidelines for developing a community noise ordinance or regulation: First steps