摘要:

Loudness levels (LL) of musical scale segments playedpianissimoandfortissimowere predicted for 11 orchestral instruments, using Zwicker’s and Stevens’ Mark VI procedures for loudness calculation. The results show that the dynamic LL range of musical instruments depends not only on the dynamic sound‐pressure level range, but is also influenced by changes in the spectral envelope that accompany the dynamic gradations of sound. As the sound is played louder, its bandwidth extends to high frequencies, and the increase in sound‐pressure level (SPL) is greater for the high partials than for the low ones. Due to spectral loudness summation, the changes in spectral envelope with playing level enhance the dynamic LL range of the sound. As a consequence, for most instruments the dynamic LL range in a given pitch register is larger than the dynamic SPL range in that register. The difference between the two ranges was found to be greatest for brass instruments and for the clarinet, and approached about 6 dB in certain pitch registers.

ISSN:0001-4966    

DOI:10.1121/1.411448

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

After a review of the structure of wood concerning its acoustic properties and a discussion of the merits and demerits of wood as a material for making soundboards of stringed instruments, the effects of three chemical treatments (a low molecular weight phenolic resin treatment, a resorcin/formaldehyde treatment, and a saligenin/formaldehyde treatment) on the acoustic properties of Sitka spruce wood are reported and compared with those of formaldehyde treatment. All three chemical treatments increased the specific dynamic Young’s modulus and greatly decreased damping (tan δ) without greatly increasing specific gravity. The range was almost equivalent to that with formaldehyde treatment whose superb effects have already been confirmed in the violin. With saligenin/formaldehyde treatment, the frequency dependence of tan δ could be controlled over a wide range by changing the saligenin concentration. In all treatments, hygroscopicity was reduced and dimensional stability was improved significantly.

ISSN:0001-4966    

DOI:10.1121/1.410600

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

The speech production system is capable of conveying an abundance of information with regards to sentence text, speaker identity, prosodics, as well as emotion and speaker stress. In an effort to better understand the mechanism of human voice communication, researchers have attempted to determine reliable acoustic indicators of stress using such speech production features as fundamental frequency (F0), intensity, spectral tilt, the distribution of spectral energy, and others. Their findings indicate that more work is necessary to propose a general solution. In this study, we hypothesize that speech consists of a linear and nonlinear component, and that the nonlinear component changes markedly between normal and stressed speech. To quantify the changes between normal and stressed speech, a classification procedure was developed based on the nonlinear Teager Energy operator. The Teager Energy operator provides an indirect means of evaluating the nonlinear component of speech. The system was tested using VC and CVC utterances from native speakers of English across the following speaking styles; neutral, loud, angry, Lombard effect, and clear. Results of the system evaluation show that loud and angry speech can be differentiated from neutral speech, while clear speech is more difficult to differentiate. Results also show that reliable classification of Lombard effect speech is possible, but system performance varies across speakers.

ISSN:0001-4966    

DOI:10.1121/1.410601

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

In this paper, the accuracy of the analysis of rapidly varying formants using spectrogram and linear prediction is assessed. Analysis of various dynamic signals shows that, when a long analysis window, like 25 ms, is used, the quality of the representation may be impoverished. Obvious unwanted effects are staircaselike formant tracks, flattening‐off of formants close to voicing onset, and bending of the formant towards a strong energy concentration in the release burst. The parameters that have the largest influence on the quality of the representation are the length of the analysis window, the transition rate of the formant, the fundamental frequency, and the position and energy of the release burst. It is shown that the most accurate analysis using a quasistationary method is made when windows are positioned pitch synchronously. Finally, a quantitative analysis of the influence of the mentioned parameters provides evidence that no deviations due to the quasistationarity assumption occur when the effective length of the analysis window is not larger than the pitch period. The wideband spectrogram is expected to be a reliable speech‐analysis tool because it meets this condition for fundamental frequencies up to 370 Hz.

ISSN:0001-4966    

DOI:10.1121/1.410602

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Most flow models used in numerical simulation of voiced sound production rely, for the sake of simplicity, upon a certain number of assumptions. While most of these assumptions constitute reasonable first approximations, others appear more doubtful. In particular, it is implicitly assumed that the air flow through the glottal channel separates from the walls at a fixed point. Since this assumption appears quite unrealistic, and considering that the position of the separation point is an important parameter in phonation models, in this paper a revised fluid mechanical description of the air flow through the glottis is proposed, in which the separation point is allowed to move. This theoretical model, as well as the assumptions made, are validated using steady‐ and unsteady‐flow measurements combined with flow visualizations. In order to evaluate the effective impact of the revised theory, we then present an application to a simple mechanical model of the vocal cords derived from the classical two‐mass model. As expected, implementation of a moving separation point appears to be of great importance for the modeling of glottal signals. It is further shown that the numerical model coupled with a more realistic description of the vocal cord collision can lead to signals surprisingly close to those observed in real speech by inverse filtering.

ISSN:0001-4966    

DOI:10.1121/1.411449

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Two experiments are presented that investigate the influence of envelope fluctuation rate upon the magnitude of comodulation masking release (CMR). In Experiment 1, thresholds were measured for a tonal signal centered in either one or five masker bands. The maskers were either narrow‐band noises or 100% sinusoidally amplitude‐modulated (SAM) tones. The five masker bands had either the same (coherent) or different (incoherent) envelopes. Envelope rate was varied by manipulating either the noise bandwidth (10–200 Hz) or the SAM rate (10–128 Hz). The CMR values were largest for slow envelope rates. In Experiment 2, envelope coherence was simultaneously manipulated at two rates by amplitude modulating (10 Hz) narrow‐band noises (100 Hz). The modulation depth was 100%, 83%, or 50%. The CMR based on the coherence of the noise carriers was about 5 dB, regardless of the SAM coherence or the modulation depth. The CMR based on the SAM coherence decreased from about 19 to 2 dB as modulation depth decreased, regardless of the noise‐carrier coherence. Thresholds were highest when the envelope fluctuations were incoherent at both rates and were lowest when the envelope fluctuations were coherent at both rates. These data suggest that the auditory system is able to make across‐frequency envelope comparisons at both envelope rates simultaneously.

ISSN:0001-4966    

DOI:10.1121/1.411450

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Results are reported from a number of experiments investigating the effects of stimulus uncertainty on the discrimination of simultaneous multitone complexes. With few exceptions the data were well described by a model in which average threshold for the detection of a change in one or more components varies with the components’ relative entropy (CoRE) in the complex [R. A. Lutfi, J. Acoust. Soc. Am.94, 748–758 (1993)]. In different experiments, thresholds for the detection of a change in target level were found to be linearly related to CoRE for manipulations in the number of targets, the number of context tones, and the relative degree of level perturbation on tones from trial to trial. The slopes of the functions did not change with measures taken at different points on the psychometric function, and in most cases were close to the theoretical value ofb=−1.0, as predicted by strict application of the model. Also as predicted (but for the exception of one listener) increasing the level of the target beyond that of the context had little or no effect on threshold. A correlational analysis of the trial‐by‐trial data revealed a tendency of listeners to give negative weight to frequencies immediately above the target, and to adjust weights in response to changes in the relative degree of level perturbation. Though inconsistent with the basic premise of the model, the variation in weights was not so great as to materially affect the predictions for mean thresholds.

ISSN:0001-4966    

DOI:10.1121/1.410607

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

These experiments were designed to explore the benefit to signal detection of different types of across‐channel cues, both alone and in combination. Some conditions were similar to those used in profile analysis (PA), and some to those used in comodulation masking release (CMR). Others were designed specifically to eliminate, or render unreliable, a particular across‐channel cue so that the benefit to performance from another cue could be assessed. Thresholds for detecting an increment in level of a sinusoid, or of the carrier of a sinusoidally amplitude modulated (SAM) sinusoid, were measured in the presence or absence of four sinusoids or SAM sinusoids (flankers), two centered above and two centered below the signal frequency. The flankers were always modulated with the same depth as the target component during nonsignal intervals. The flankers, when present, were either equal in level to the nonsignal target sinusoid, or were scrambled in level (different in level both from each other and from the target by an amount that varied randomly from one stimulus to the next). In some conditions the overall level of the stimuli was also varied randomly from one stimulus to the next. The results indicate that about 5–6 dB of benefit arises from the cue of a disparity in level across frequency (a PA‐type cue), and about 1–3 dB from the cue of a disparity in envelope modulation depth across frequency (a CMR‐type cue). For some subjects, slightly less benefit occurred when the flankers were presented to the opposite ear as the signal, requiring across‐ear comparisons. Scrambling the level of the flankers often impaired performance, especially when the overall level of the stimuli was fixed. This appears to reflect an across‐channel interference effect.

ISSN:0001-4966    

DOI:10.1121/1.411451

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

The illusion of auditory apparent motion (AAM) was examined in order to determine the burst durations and interstimulus onset intervals (ISOIs) at which AAM is heard when spatial information regarding source location was varied. In the first experiment AAM was examined in the free field under monaural and binaural listening conditions. AAM was heard at the same burst duration‐ISOI combinations for both listening conditions, but the location of the lead source could be determined only under binaural listening. In the second experiment AAM was measured with two and three sound sources. The number of sources did not affect the burst duration‐ISOI combinations that produced AAM, but did affect the determination of the location of the lead source. In the third experiment AAM was tested when the sources were located in the median plane. The sources were located either at 0° and 180° azimuth, or both at 0° azimuth, one in the horizontal plane and one 20° above. The location of the speakers did not affect the timing requirements for the perception of AAM, only the timing requirements for the detection of the lead source. In the fourth experiment, AAM was measured when the vertical separation between the sources was either 2.5° or 20°. AAM was heard at both separations, even though 2.5° is less than the vertical MAA. In each of these experiments only burst duration and ISOI determined whether motion was heard. Localization cues were important only for the determination of the direction of motion.

ISSN:0001-4966    

DOI:10.1121/1.411452

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP

摘要:

Previously, it was shown [Donetal., J. Acoust. Soc. Am.94, 2135–2148 (1993)] that cochlear response times are gender specific and about 13% shorter in females than in males. It is also suggested that one of the possible reasons click‐evoked auditory brainstem response (ABR) waveforms recorded from females are better defined and have larger amplitudes than those of males is due to a sex difference in cochlear response times leading to better synchronization of the cochlear output across the frequency regions. Variability in cochlear response times would also lead to variability in click evoked ABR amplitudes. The high‐pass noise masking derived ABR technique was used to investigate the effect of normalizing the individual temporal variability at the neural and cochlear levels. This involved adjusting for differences in neural conduction time (I–V delay) by a compression or expansion of the derived ABR waveforms and by adjusting for differences in cochlear response times by a shift of the derived ABR waveforms. A summation of the compressed and shifted ABRs results in a normalized unmasked ABR waveform that can then be compared for amplitude variability with the unprocessed unmasked ABRs. Compensation for the neutral I–V variability had little effect while compensation for cochlear response times, particularly the delay between the 5.7‐ and 2.8‐kHz regions, greatly affected the amplitude of wave V of the compounded ABR. This work provides a better understanding of the significant relationship between cochlear response times and variability of the ABR peak amplitudes.

ISSN:0001-4966    

DOI:10.1121/1.410608

出版商:Acoustical Society of America    

年代:1994

数据来源: AIP