Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 279
Hearing Loss: Determining Eligibility for Social Security Benefits Appendix B American National Standards on Acoustics The content of each of ten standards of the American National Standards Institute (ANSI) pertaining to bioacoustics (S3) and referenced in this report is briefly described here. The standards can be obtained from the Acoustical Society of America (ASA), Standards Secretariat, 35 Pinelawn Rd., Suite 114E, Melville, NY 11747, or https://asastore.aip.org/ (under S3 Bioacoustics). ANSI S3.1-1999 (R2003) American National Standard Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms. This Standard specifies maximum permissible ambient noise levels (MPANLs) allowed in an audiometric test room that produce negligible masking (less than or equal to 2 dB) of test signals presented at reference equivalent threshold levels specified in American National Standard S3.6-1996 American National Standard Specification of Audiometers. The MPANLs are specified from 125 to 8000 Hz in octave and one-third octave band intervals for two audiometric testing conditions (ears covered and ears not covered) and for three test frequency ranges (125 to 8000 Hz, 250 to 8000 Hz, and 500 to 8000 Hz). The Standard is intended for use by all persons testing hearing and for distributors, installers, designers, and manufacturers of audiometric testrooms. This standard is a revision of ANSI S3.1-1991 American National Standard Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms ANSI S3.4-1980 (R2003) American National Standard Procedure for the
OCR for page 280
Hearing Loss: Determining Eligibility for Social Security Benefits Computation of Loudness of Noise. This standard specifies a procedure for calculating the loudness of certain classes of noise. In applications of the procedure, it is assumed that the spectrum of the sound has been measured in terms of sound pressure levels in 1/3-octave or 1/1-octave bands in either a diffuse or free field. The procedure is derived from three empirical relations: (1) A set of equal-loudness contours for bands of noise in a diffuse sound field. (2) A rule relating the total loudness of a sound to the loudness indexes of the frequency bands composing it. (3) A loudness function relating loudness in sones to loudness level in phons. This relation is such that loudness is a simple power function of sound pressure at 1000 Hz. On the basis of these empirical relations, the total loudness of a sound may be calculated with the aid of a table or a chart, together with a linear equation. (An appendix provides a computer program in the FOR-TRAN language for calculations based on 1/3-octave band sound pressure levels.) Loudness as herein computed, depends upon the acoustic properties of a sound that impinges upon a normal-hearing listener. Loudness is also a prime determinant of a person’s affective response to sound. The affective response may be expressed in terms such as noisiness, annoyance, and unacceptability. An appendix describes the extent to which the procedure of this standard applies to subjective judgments of noise made in the laboratory when listeners are instructed to judge aspects of the sound other than loudness. ANSI S3.5-1997 (R2002) American National Standard Methods for Calculation of the Speech Intelligibility Index. This Standard defines a method for computing a physical measure that is highly correlated with the intelligibility of speech as evaluated by speech perception tests given to a group of talkers and listeners. The measure is called the Speech Intelligibility Index, or SII. The SII is calculated from acoustical measurements of speech and noise. This standard is not a substitute for ANSI S3.2-1989 (R1995) American National Standard Method for Measuring the Intelligibility of Speech over Communications Systems. ANSI S3.6-1996 American National Standard Specification for Audiometers. The audiometers covered in this specification are devices designed for use in determining the hearing threshold of an individual in comparison with a chosen standard reference threshold level. This standard provides specifications and tolerances for pure-tone, speech, and masking levels and describes the minimum test capabilities of different types of audiometers. The standard also specifies standardized threshold for detecting pure tones. ANSI S3.13-1987 (R2002) American National Standard Mechanical Cou-
OCR for page 281
Hearing Loss: Determining Eligibility for Social Security Benefits pler for Measurement of Bone Vibrators. This standard specifies requirements for mechanical couplers used for calibrating bone-conduction audiometers and making measurements on bone vibrators and bone-conduction hearing aids. Specific design features are given for the mechanical coupler when driven by a vibrator with a prescribed plane circular tip area and applied with a specific static force. An appendix provides an example of a specific construction of a mechanical coupler. ANSI S3.21-1978 (R1997) American National Standard Methods for Manual Pure-Tone Threshold Audiometry. Pure-tone threshold audiometry is the procedure used in the assessment of an individual’s threshold of hearing for pure tones. Pure-tone threshold audiometry includes manual air-conduction measurements at octave intervals from 250 through 8000 Hz and at intermediate frequencies as needed. When abrupt differences of 20 dB or more occur between adjacent octave frequencies, additional frequencies may be included at the discretion of the tester. Bone-conduction measurements may be carried out if indicated by the test requirements at octave intervals from 250 through 4000 Hz. Also, when required, masking is to be used. The purpose of this standard is to present procedures for conducting manual pure-tone threshold audiometry whose use will minimize intertest differences based on test method. ANSI S3.22-2003 American National Standard Specification of Hearing Aid Characteristics. This standard describes air-conduction hearing-aid measurement methods that are particularly suitable for specification and tolerance purposes. Among the test methods described are output sound pressure level (SPL) with a 90-dB input SPL, full-on gain, frequency response, harmonic distortion, equivalent input noise, current drain, induction-coil sensitivity, and static and dynamic characteristics of automatic gain control (AGC) hearing aids. Specific configurations are given for measuring the input SPL to a hearing aid. Allowable tolerances in relation to values specified by the manufacturer are given for certain parameters. Appendices are provided to describe equivalent substitution methods, characteristics of battery simulators, and additional tests to characterize the electroacoustic performance of hearing aids more completely. ANSI S3.39-1987 (R2002) American National Standard Specifications for Instruments to Measure Aural Acoustic Impedance and Admittance (Aural Acoustic Immittance). This standard provides specifications for instruments designed to measure acoustic impedance, acoustic admittance, or both quantities, within the human external ear canal. Terms that apply to these instruments and to related measurements are defined. Four types of instruments are classified. Characteristics, specifications, and recommended
OCR for page 282
Hearing Loss: Determining Eligibility for Social Security Benefits calibration procedures then are provided. Material within this standard is intended both for users and for manufacturers of instruments that measure aural acoustic impedance and admittance. ANSI S3.42-1992 (R2002) American National Standard Testing Hearing Aids with a Broad-Band Noise Signal. This standard describes techniques for characterizing the steady-state performance of hearing aids with a broadband noise signal. The need for such a standard arises from the importance of assessing the performance of hearing aids in environments more nearly representing their real-world use. The noise test signal specified herein has been employed by the National Bureau of Standards for over 20 years in testing hearing aids. Among the tests described are noise saturation SPL, noise gain, frequency response, family of frequency response curves, and output versus input characteristic. Additionally, the appendix recommends use of the coherence function to indicate the validity of frequency response measures and distinguishes between use of random and pseudo-random noise and asynchronous versus synchronous analysis. ANSI S3.46-1997 (R2002) American National Standard Methods of Measurement of Real-Ear Performance Characteristics of Hearing Aids. This standard provides definitions for terms used in the measurement of real-ear performance characteristics of hearing aids, provides procedural and reporting guidelines, and identifies essential characteristics to be reported by the manufacturer of equipment used for this purpose. Acceptable tolerances for the control and measurement of SPLs are indicated. Where possible, sources of error have been identified and suggestions provided for their management.
Representative terms from entire chapter: