Volume 69, Issue S1, May 1981
Index of content:
- PROGRAM OF THE 101ST MEETING OF THE ACOUSTICAL SOCIETY OF AMERICA
- Session G. Speech Communication I: Acoustic Analysis
- Contributed Papers
69(1981); http://dx.doi.org/10.1121/1.2143547View Description Hide Description
Thanks to the development of fast digital hardware performing real‐time spectral analysis on speech data, dependable pitch analysis can be obtained even in the presence of a large amount of noise through the use of new F 0 measurement techniques. A new method is presented here, based on the crosscorrelation between the power spectrum of suitably windowed speech data F(ω) and a comb function . The comb function detects the possible harmonic structure in the spectrum, so that when C(ω p ,ω) is carefully chosen, the crosscorrelation function I(ω p ) shows maxima at values of ω p corresponding to the fundamental frequency of voiced speech. The appropriate design of the comb (with an amplitude varying with ω), leads to more appropriate and economical digital hardware compared to the general crosscorrelation approach.
- Session D. Architectural Acoustics I: General
69(1981); http://dx.doi.org/10.1121/1.385964View Description Hide Description
This paper presents the results of preliminary measurements of the difference between the incident sound levels at the front and rear facades of suburban detached and semi‐detached houses adjacent to major roadways. The measurements also yielded data on sound transmission through open windows and comparisons between the sound levels measured in open windows, at the surface of the building facade, and at 2 m from the facade.
69(1981); http://dx.doi.org/10.1121/1.385965View Description Hide Description
The angle of incidence is a major variable for calculating transmission loss from field data [ASTM 336 77]. This suggests that the acoustical insulation of residential construction vary with the relative location of the flight paths and the housing. Alternatively, the number of reflected paths in normal residential areas may be so great as to override any such effect. This paper tests the hypothesis that the acoustical insulation of residential construction is affected by location relative to the flight path, using field transmission loss data collected during summer 1980 for thirty rooms in the Toronto area. Two cases are compared. In the first, the flight path is perpendicular to the plane defined by the element of interest, while in the second, the flight path is parallel to the same plane. Road traffic sites are also used as they are similar to the second case. For the first set of cases, the acoustical insulation for different sections of each flyover is also studied.
69(1981); http://dx.doi.org/10.1121/1.385966View Description Hide Description
Development of a device for modeling of multiple reflections in two‐dimensional representations of rooms. The self‐contained unit developed employs a fixed laser, the beam of which is rotated using a motorized front‐surface mirror, a steel plate to which plan or section drawings of rooms can be attached with magnets and a selection of mirror units, magnet attached, which can be rapidly re‐oriented to change the room geometry. Multiple reflections from low‐power lasers can be difficult to see; to overcome this problem, the beam is made visible by means of a smoke generator introducing smoke into a forced‐draft, closed‐loop, recirculation system, which includes the simulation chamber. The simulation chamber is accessed by a vertical sliding window, safety‐interlocked to prevent exposing users to the laser beam, and the window itself protects observers from the beam since it strikes the glass at an angle which is less than the critical angle. The device makes fifth and higher order reflections visible and, due to the safety features incorporated, is suitable for classroom use, as well as for auditorium reflection pattern analysis.
69(1981); http://dx.doi.org/10.1121/1.385967View Description Hide Description
A low‐cost hemi‐anechoic laboratory for machine noise measurement is described. The special difficulties in qualifying tests of a hemi‐anechoic chamber were resolved using Moreland's procedure (NOISE‐CON 79 Proceedings, 365–372). These tests disclosed anomalies in the free field characteristics near 250 Hz, which were traced to even spacing of the sound absorptive wedges. These anomalies were reduced by splitting the space between wedges with absorptive dividers. The conclusion is drawn that regularities in wedge size or spacing must be particularly avoided when such test chambers are to be used for measurement of pure tones.
Second‐order statistics of finite estimation of the spatial variance and time averaging in a reverberation chamber with a rotating diffuser69(1981); http://dx.doi.org/10.1121/1.385968View Description Hide Description
The accuracy of measuring the sound power that a source radiates into a reverberation chamber is directly related to the precision of the finite space‐time average of the pressure squared. It is well known that a rotating diffuser reduces the normalized spatial variance of the pressure squared in a reverberation chamber excited by a pure tone. The relative decrease of the spatial variance by the rotating diffuser has been called the “figure of merit.” Determination of the F.O.M. therefore depends on the finite sample size estimate of the normalized spatial variance. The statistics of the finite sample size spatial variance estimate will be discussed and confidence levels will be shown. Time averaging requirements of the pressure modulus for the rotating diffuser modulation process will be presented for both linear and exponential averaging.
69(1981); http://dx.doi.org/10.1121/1.385969View Description Hide Description
An analysis of the relationship between source location and measuredsound power output of discrete frequency sources in reverberation rooms is presented, based on data obtained during the qualification of the 94 m3reverberation room at the Centre for Building Studies. Total measurementuncertainty is evaluated at several source positions for both a bare chamber and for the final configuration with a rotating diffuser and low‐frequency absorption. A high total measurementuncertainty at low frequencies proved to be the major obstacle to qualification as has been observed in numerous other studies (see for example the Sept.–Oct. 1976 issue of Noise Control Engineering). The modifications to the room and averaging over some positions reduced the measurementuncertainty to acceptable limits. It was observed that source position averaging was ineffective for the bare chamber configuration as pressure/frequency responses were highly correlated for different source positions. The addition of diffusing elements and low‐frequency absorption increase modal overlap and result in less correlated pressure/frequency responses between source positions and hence improve the averaging effectiveness. [Work supported by NSERC.]
69(1981); http://dx.doi.org/10.1121/1.385970View Description Hide Description
New chemistry laboratories require variable air volume systems to meet high exhaust airflow requirements and to reduce energy consumption during varied duty loads. Limited building budgets often introduce shortcuts into these systems that compromise the noise and vibration environments for chemists and their increasingly sensitive instrumentation. If acoustical planning is not included in the initial design, remedial noise and vibration controls will probably be limited, time‐consuming, and expensive to implement. Three chemistry laboratories that required acoustical evaluation and remedial controls following recent building construction serve as case studies. Noise and vibration sources discussed include variable air volume supply fans, exhaust air fans, walk‐in and counter‐top exhaust hoods, and their respective ductwork and control systems.
- Session PP. Speech Communication VII: Perception I (Poster Session)
Interactive role of formant transitions and steady‐state spectral characteristics in the perceptual identification of nasal consonants69(1981); http://dx.doi.org/10.1121/1.385971View Description Hide Description
Test sequences with VC stimuli for V = /a/ and C = unreleased /n, ɲ,ŋ/, were prepared using a software serial formantsynthesizer. Transition ending point frequency values and nasal steady‐state spectral patterns for /an/,/aɲ/, /aŋ/ were chosen as fixed and variable parameters and combined reciprocally. Several speakers of a language (Catalan) that allows the presence of unreleased /n, ɲ,ŋ/, in absolute final position took the perception test. Preliminary results indicate that while steep rising F2 and F3 transitions are the main perceptual cues for /ɲ/ identification, an optimal pattern of steady‐state resonances and antiresonances is essential for /ŋ/ recognition. Appropriate transition and spectral characteristics are needed for a satisfactory /n/ identification. These findings are related to two important facts of acoustic theory of speech production: acoustic stability corresponding to substantial articulatory changes at place of palatal constriction and distinctive acoustic effects shown by the oronasal cavity system for /ŋ/. Further research on the phonemic identification of the palatal stimuli is to be done with speakers of American English.
- Session KK. Speech Communication VI: Prosodies and Synthesis
69(1981); http://dx.doi.org/10.1121/1.385972View Description Hide Description
SYNTH is a rather conventional software serial two‐branch formantsynthesizer, employing techniques developed by Rabiner, Rothenberg, and others. We have tried to make its control as convenient and its operation as transparent as possible for the phoneticresearcher. The vowel branch, excited by noise and/or a glottal waveform, has three variable and two fixed poles, and optionally, a variable zero (for lateral sounds) or zero and pole (for nasalized sounds). The consonant branch, excited by noise that can be modulated according to the glottal output (for voiced fricatives), has a variable zero and pole. Transfer‐function polynomial coefficients are calculated pitch‐synchronously. All routines are programmed (for the PDP 11/45) in FORTRAN—IV Plus, except for a few computationally intensive functions coded in assembly language. Fixed parameter values are collected in one modifiable file. SYNTH is called by an executive program (SYN) that also enables editing, storage, and graphic and numerical display of variable and fixed parameter values and output PCM waveforms. [Supported by NSF and VA.]
- Session EE. Underwater Acoustics V: Propagation, Scattering and Signal Processing (Part Lecture, part Précis‐Poster Session)
- Precis Poster
69(1981); http://dx.doi.org/10.1121/1.385973View Description Hide Description
The effects of sound‐speed variations produced by shallow (less than about 300 m) deep‐ocean fronts on short‐range transmission between surfaced source and receiver are investigated using ray theory. A parametric model of such fronts, based on observational data, is constructed via sound‐speed profiles which are trilinear with depth. The model is sufficiently general to permit determination of acoustical effects for fronts of varying strengths, vertical extents, and positions relative to the propagation range. Frontal influences on travel time and geometrical spreading loss are examined, and expressions for per‐ray amplitude and phase are developed. Then, the dependence of total‐field amplitude and phase for cw transmissions on frontal strength, vertical extent, and relative location are determined. All these frontal quantities are demonstrated to produce significant acoustical variations, such as total‐field intensity changes of more than 6 dB depending on frontal location. Simple and accurate approximations to both per‐ray and total‐field variations are presented which could be useful in predicting changes in these quantities due to shallow fronts. [Work supported by ONR.]
- Session X. Engineering Acoustics IV and Noise IV: Sound Attenuation in Flow Ducts
- Contributed Papers
69(1981); http://dx.doi.org/10.1121/1.385974View Description Hide Description
The state‐of‐the‐art of using sound absorbers in ducts is almost entirely limited to the analysis and testing of uniform, locally reacting linings. There is, however, a growing concern that this might lead to designs which are far from optimum. One form of non‐uniformity which is expected to be beneficial is that along the circumferential direction. One great difficulty in implementing this concept is lack of availability of separable solutions. As a result, extremely costly numerical techniques are being tried. This paper shows that in many cases, such techniques are unnecessary. For a general sinusoidal variation in the absorbent properties, in the circumferential direction, closed‐form solutions could be obtained. These solutions are non‐separable. The solutions show that it might be possible to convert a lower circumferential order mode into a higher order one, which might be easier to attenuate.
- Session T. Engineering Acoustics III and Physiological Acoustics III: Middle Ear Engineering
- Invited Papers
Modeling reverse middle ear transmission: Aural acoustic distortion products, “echoes,” and spontaneous emissions69(1981); http://dx.doi.org/10.1121/1.385975View Description Hide Description
Since 1978, when Kemp reported the existence of stimulated acoustic emissions from within the human auditory system [J. Acoust. Soc. Am. 64, 1386–1391], several studies have indicated that acoustic signals originating within the cochlea propagate through the middle ear into the ear canal. We have used nonlinear cochlear mechanical models to interpret distortion products observed both in the acoustic signal in the ear canal and in the response patterns of single cochlear nerve fibers. In addition to a nonlinear cochlear model, our modeling system includes a bidirectional middle earmodel and an acoustic coupler model; these additional elements are needed in order to make quantitative comparisons between model results and the experimental observations, The mechanical middle earmodel we have developed is based on experiments measuring the forward transmission characteristics of the auditory systems of cats [e.g., Guinan and Peake, J. Acoust. Soc. Am. 41, 1237–1261 (1967)], and is adequate for frequencies below 3 kHz. In order to extend the model to higher frequencies a more elaborate representation of the motion of the eardrum will have to be included. Our model results give indirect support for the adequacy of our middle earmodel with respect to reverse transmission, but direct experimental measurements of reverse transmission properties of the middle ear are needed. [Supported by NIH grants NS07498, RR00396, NS00162, GM01827.]
- Session O. Underwater Acoustics III: Propagation (Part Lecture Part Précis‐Poster Session)
- Contributed Papers
A further study of the space and time stability of a narrow‐band acoustic signal in the ocean: Intermediate range results69(1981); http://dx.doi.org/10.1121/1.385976View Description Hide Description
The initial analysis of a narrow‐band signal was conducted for a source‐receiver distance of 1000 km [D. G. Browning, J. Acoust. Soc. Am 68 (S1), S72(A) 1980]. Although the bandwidth remained relatively narrow (∼3 mHz) it appeared there were distinct frequency components that could be associated with separate ray groups. In order to verify this, a similar analysis has been conducted at an intermediate range (125 km) where preliminary results indicate that the components may be resolvable. Space and time variability are given for percentage Doppler shift, bandwidth and intensity. The results are compared to predictions obtained from the FACT Option of the Generic Sonar Model. [Work supported by DARPA].
- Session I. Psychological Acoustics II: Masking
69(1981); http://dx.doi.org/10.1121/1.385977View Description Hide Description
In most dichotic experiments, sounds played to each ear are drawn from the same set, i.e., masking signals are drawn from the same catalog as the target signals. We wish to consider the possibility of using maskers that are not identical to the target sound set. We have tested the influence of a series of maskers on identification of tonal patterns, with masker presented simultaneously and contralaterally to the target signal. Maskers were designed to sample the range from performance with monaural presentation (i.e., no masker) to performance in the situation where masker catalog is the same as target catalog (the traditional “dichotic listening” arrangement). Maskers studied included: Noise or tone gated on and off with the target, sounds mimicking the temporal fine structure of the target, etc. We have found that: (1) Such maskers can be used to reveal ear differences of the magnitudes found in more traditional dichotic designs, and (2) manipulation of the physical characteristics of the masker may prove a means of studying the psychoacoustical dimensions of some types of complex sounds. [Work supported by NINCDS NS 03856.]
- Session BBB. Speech Communication IX: Perception III: Developmental, Language‐ and Hearing‐Impaired, and Vibrotactile
The effect of compression limiting on the speech intelligibility of sensorineural hearing impaired listeners69(1981); http://dx.doi.org/10.1121/1.385978View Description Hide Description
The purpose of this study was the evaluation of multiband compression limiting designed to protect hearing‐impaired listeners from high‐level speech and environmental sounds. The relative performance of two linear and four compression‐limiting systems has been measured for two subjects with flat sensorineural losses. The test materials, consisting of nonsense CVC syllables spoken by male and female speakers, were presented over a 30‐dB range of input levels. The subjects chose an overall listening level consistent with both maximum intelligibility over the range of input levels and long‐term listening comfort. Preliminary results indicate that both higher average presentation levels and increased speech intelligibility scores are associated with compression limiting relative to linear amplification. [Work supported by NIH.]
- Session YY. Speech Communication VIII: Perception II: Dichotic Listening, Acoustic Cues
69(1981); http://dx.doi.org/10.1121/1.385979View Description Hide Description
Trained listeners were asked to discriminate, in a four‐level 2AFC paradigm, the interval separating two tone burst markers. The total duration of the first marker was 10 ms (2‐ms rise and fall times), whereas that of the second marker was 100 ms (with a 2‐ms rise and a 10‐ms fall time). The duration of a gap just discriminable from a nominally 0‐ms gap was about 1 ms when the frequency of the two markers was identical (1 kHz). On the other hand, thresholds wet about ½ to 1½ orders of magnitude higher when the two frequencies differed by 2 octaves (2000 and 500 Hz, respectively). These data confirm earlier results. [Divenyi and Sachs, Percept. Psychophys. 24, 429–436 (1978)]. In the remaining conditions the first marker was a 10‐ms tone burst of 2 kHz, while the second marker was a 100‐ms tone burst starting with a frequency sweep toward a terminal frequency. This sweep either started at 2 kHz and ended 2 octaves lower at 500 Hz (i.e., the sweep moved away from the frequency of the first marker) or vice versa (i.e., the sweep moved toward the frequency of the first marker). Several sweep durations (10, 30, 50, and 100 ms) were used. Gap discrimination thresholds were found to be in the 1‐ms range regardless of the direction of the frequency sweep in the second marker as long as the duration of the frequency transition was no longer than 30 ms. The threshold remained similarly low for the longer sweep durations whenever the frequency of the second marker started at that of the first and then moved away from it. On the other hand, gap thresholds became higher in those conditions in which the duration of the transition was 50 ms or longer, and the frequency of the second marker moved toward that of the first but started at a frequency 2 octaves below. The results appear to bear relevance to the time window of auditory analysis, on the one hand, and to the perception of CV formant transitions, on the other. [Work supported by NINCDS and the Veterans Administration.]
- Session WW. Engineering Acoustics VI: Acoustics in Telecommunications II
69(1981); http://dx.doi.org/10.1121/1.385980View Description Hide Description
Sound striking an electret transmitter's movable electrode or diaphragm yields a capacitance variation in an adjacent air gap, wherein a biasing electrostatic field is modulated. That field is shown to be produced by a fixed electret charge implanted near the surface of a solid dielectric within the device.Electret principles such as equivalent voltage are described analytically. A transmitter mathematical model is depicted including the mechanacoustic structure, the transduction, and the preamplifier. It is approximated by an equivalent electrical circuit with four degrees of freedom. The appropriate derivation of diaphragm lumped parameters for a capacitive‐type transducer is discussed. The role of frequency response criteria peculiar to telecommunications and diaphragm electrostatic stability limitation as they affect parameter optimization is outlined. A thermal stabilization procedure is described which minimizes long‐range viscoelastic changes in a metallized Teflon® (registered—E. I. DuPont) diaphragm's mechanical response. The history of the condenser and electretmicrophones will be briefly reviewed. Modern electret advantages over carbon microphones will be outlined including dc power consumption, size, electroacoustic linearity, and mechanical vibration sensitivity.
- Session BBB. Speech Communication IX: Perception III: Developmental, Language‐ and Hearing‐Impaired, and Vibrotactile
69(1981); http://dx.doi.org/10.1121/1.385981View Description Hide Description
In this study physical measurements of talkers' lips during production of CVC monosyllables were correlated with perceptual confusions among the utterances during lipreading. Five talkers were videotaped producing a large set of CVC's with /f,v,w,r,p,b,t,d,h,g/ as consonants and /i,ɪ,a,ᴜ,u/ as vowels. Tracings were made from the tape and intelligibility of lipreading was determined by normal and hearing‐impaired viewers. It was found that in contexts with minimal labial coarticulation the variance in vowel confusions was almost completely explained by static measurements of lip height and width at the point of maximal vowel constriction. In bilabial, rounded, and labio‐dental contexts, however, it was found that (a) overall intelligibility of the vowel was reduced, (b) lip height and width predicted a high percentage of the perceptual confusions among the vowels, but vowel duration and lip trajectory improved the prediction in some cases, and (c) considerable variation existed among talkers and the intelligibility of individual talkers could be predicted by a small set of measurements of the lips during vowel production. [Work supported by Department of Clinical Investigation, WRAMC.]
- Session PP. Speech Communication VII: Perception I (Poster Session)
69(1981); http://dx.doi.org/10.1121/1.385982View Description Hide Description
Sung vowels provide an excellent opportunity to study the information present in the vowel steady state. Ten American English vowels /i,I,e,ɛ,æ,ɑ,ʌ,o,U,u/ in /b/‐vowel‐/d/ syllables were sung by; a professional male singer at seven different pitches: C3, E3, A3, C4, E4, A4, and C4. Syllable length ranged from about 500 to 900 ms. An algorithm was used to extract an approximately 200‐ms sample of the steady‐state portion, carefully avoiding initial and final consonant transitions. Listeners attempted to identify the vowel using only this steady‐state information. Removal of the consonantal context increased vowel identification errors. In addition, identification accuracy was lower for vowels sung at the higher pitches. The error rate was greater for back vowels than for front vowels, especially at the higher pitches. Confusions between /ɑ/ and /ʌ/ were especially common. The effect on vowel identification of using a “chest” voice versus a “head” voice was also investigated. Results are discussed with regard to the adequacy of steady‐state information for vowel identification. [Work supported by NIMH, NICHHD, and NSF.]