摘要:

Acoustical design criteria for the recently completed St. Mary's Cathedral, San Francisco, reflect current emphasis on improved speech communication, rather than the extreme reverberance traditionally characteristic of cathedrals. By judicious placement of absorption treatment, mid‐frequency reverberation time was held down to 2.4 sec fully occupied or 4.0 sec empty, and the resulting environment was found to be most acceptable for organ and choral music. Good speech communication was achieved by an electronic reinforcement system that directed most of its energy toward the congregation without adding much to reverberant levels.

ISSN:0001-4966    

DOI:10.1121/1.1913583

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The sound attenuation provided by 11 wood‐framed floor‐ceiling assemblies with troweled floor toppings is presented. Three tests of assemblies with nailed gypsum board ceilings provided sound transmission class (STC) values of 48 to 50. By comparison, seven assemblies with ceilings applied on resilient channels and one with a suspended ceiling gave STC values of 55 to 59. The addition of glass fiber in the joist space, or the substitution of factory‐fabricated, plywood‐web joists for solid wood joists, provided less impressive improvements in STC values. Tests of three assemblies with vinyl tile floor covering and with pad and carpet provided an impact sound insulation class (IIC) of 50 to 52 with tile and 72 to 77 with carpet. The improvements in IIC that were anticipated from other changes in the floor‐ceiling assemblies were clouded by the measuring and rating system. The need for a method other than the current ISO/R140 international standard for realistically measuring and rating resistance to impact sound transmission is emphasized by results of these tests.

ISSN:0001-4966    

DOI:10.1121/1.1913584

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A theory has been developed which can be used to quantify the loss of synchronization in auditory nerve discharges with increasing stimulus frequency.The assumptions for the theory are (1) the probability of discharge versus time position within the period for very low stimulus frequency has the shape of a half‐wave‐rectified sine wave, and (2) travel times for impulses propagating along the acoustic nerve have a Gaussian statistical distribution around some mean travel time. With these two assumptions it is possible to predict the shapes of histograms which arise from higher frequency stimulation. Further, a single quantity (Gt) may be derived from these fits which characterizes the whole progression from pure half‐sine‐wave distribution at zero frequency to a completely flat distribution at high frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1913585

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Eight cats were trained to localize the source of tonal signals, presented in a free field. Tones of six different frequencies, in octave steps from 250 Hz to 8 kHz, were used. The angle at which an animal's performance was 75% correct was defined as the threshold for minimal detectable angle. This localization threshold was obtained for each cat at each frequency. Across frequencies the localization thresholds changed little from 250 Hz to 2 kHz, then increased greatly at 4 kHz and decreased again at 8 kHz. Similarities and differences in the performance of man and cat in localizing pure tones are discussed in relation to the possibility that the cat, like man, uses differences in binaural time and in binaural intensity as the principle cues for sound localization.

ISSN:0001-4966    

DOI:10.1121/1.1913586

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

The ear can discriminate between two transient signals that have identical energy spectra but different phase spectra (hence different waveshapes) as long as the total duration of the signals exceeds about 2 msec. A natural question, but one impossible to answer on the basis of previous work, which used transient signals having a broad energy spectrum, is whether this value for temporal acuity is dependent on the frequency content of the signal. Two types of experiments were conducted to answer this question. In one experiment, the energy spectrum was broad but the temporal cues were restricted to specific regions of the frequency spectra. In the second experiment, two segments of a sinusoid (one 10 dB more intense than the other) was played in one order on the reverse. Both experiments confirm the finding that the value of temporal acuity is about 2 msec and that this value is largely independent of frequency. Also of interest is the fact that for the sinusoidal signals the percentage of correct discriminations of temporal order is a nonmonotonic function of the total duration of the two segments.

ISSN:0001-4966    

DOI:10.1121/1.1913587

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

An experiment was conducted in order to determine the changes in loudness brought about by electro‐cutaneous elicitation of the middle‐ear reflex. Subjects were required to judge the relative loudness of the second of three consecutive 30‐msec bursts of tone, the second tone being accompanied by an electrical shock to the external auditory meatus, capable of eliciting a contraction of the middle‐ear muscles. The difference between these judgments and those of the control condition (shock on the arm) was taken to represent a measure of the attenuation provided by contraction of the middle‐ear muscles. Test tones were 500, 1000, 2000, and 3000 Hz at levels of 65, 75, 85, 95, and 105 dB (rezero hearing loss). The results indicate that the middle‐ear reflex decreases the middle‐ear's transmission mainly for low‐frequency sounds. The results fail to lend support to the Loeb‐Riopelle hypothesis that the middle‐ear reflex acts as a limiter, rather than a linear attenuator. In fact, there was a small, but significant, decrease in attenuation with increasing auditory stimulus intensity at the higher frequencies.

ISSN:0001-4966    

DOI:10.1121/1.1913588

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

Predictions of the correlation model of binaural masking‐level differences (BMLDs) are presented for the class of experiments in which the noise waveforms at the two ears are identical, while the tonal‐signal parameters for interaural amplitude ratio and interaural phase shift are varied. These predictions are compared to empirical data, and their relations to predictions of the equalization‐cancellation model and a lateralization model are discussed.

ISSN:0001-4966    

DOI:10.1121/1.1913589

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

It is known that a greater attenuation is required for judgments of half‐loudness with speech than for half‐loudness with steady‐state sounds. This study explored the role of reverberation in the anomalous loudness function of speech. Comparison stimuli were prepared by electrical attenuation of the standard stimuli, keeping the proportion of reverberant to direct components fixed for any particular judgment. A total of 1110 subjects were tested with speech or with isolated speech sounds, using a single judgment procedure employed in earlier studies designed to minimize known experimental biases. Changes in reverberation produced profound changes in loudness functions. Estimates of the loudness of speech resemble estimates of acoustic perspective, both being based upon the ratio of direct to reverberant sound as well as the intensity of these components. Evidence indicates that judgments of half‐loudness of speech (as well as half‐loudness of isolated speech sounds, noises, and tones) are equivalent to estimates of the effect of doubling distance from listener to sound source: The anomalous loudness function for speech is attributable to the special role of reverberation with this stimulus. These conclusions are in agreement with the physical correlate theory of sensory intensity.

ISSN:0001-4966    

DOI:10.1121/1.1913590

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

It has often been suggested that the pitch of a complex tone is given by the inverse of the time between peaks in the fine structure of the stimulus waveform. This paper argues that in view of recent empirical evidence such a position is untenable. Fine‐structure models of pitch such as the “peak‐picker” are phase sensitive; they predict that changes in stimulus fine structure will be accompanied by changes in pitch. Results from several pitch‐matching experiments do not support this prediction. Two experiments are described in which pitch matches were made to complex‐tone stimuli presented in several different phase configurations. In both experiments the distributions of pitch matches appeared to be the same for all phase configurations. Stimulus fine structure, of course, changed dramatically with phase. Of course, the fact that pitch is insensitive to the relative phases of the stimulus components does not mean that listeners cannot hear the phase changes. In many cases stimuli with the same pitch are perfectly discriminable. It is only pitch that appears to be insensitive to details of wave form fine structure. This leads us to reject the simple fine‐structure theories of pitch.

ISSN:0001-4966    

DOI:10.1121/1.1913591

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP

摘要:

A new approach to pitch perception is outlined in this paper. It is based on what might be called auditory pattern recognition. The general approach is formalized in a mathematical model, the so‐called “pattern‐transformation model.” In this model an acoustic stimulus is first transformed by the sense organ into a pattern of peripheral neural activity. This peripheral pattern is assumed roughly to represent the power‐spectrum of the stimulus. Thus, the temporal fine structure of the stimulus is virtually ignored; the model is phase insensitive. The peripheral pattern is then assumed to be Fourier transformed into another pattern of activity. This second pattern roughly represents the autocorrelation function of the stimulus. Pitch is derived from the positions of maximal activity in this pattern. From preliminary tests it appears that the model can successfully predict the pitch of many types of complex stimuli. In addition, the model provides estimates of pitch “strength” or “clarity.” These estimates also agree, at least qualitatively, with available data.

ISSN:0001-4966    

DOI:10.1121/1.1913592

出版商:Acoustical Society of America    

年代:1973

数据来源: AIP