摘要:

This article describes an experimental study of the motion of the grand piano key and hammer. The motions were registered by means of an optical position measuring system. The measurements include typical key and hammer motions at different dynamic levels and for different types of ‘‘touch.’’ Also, the accelerating force on the hammer before release (‘‘let‐off’’), and the following free motion of the hammer were investigated. Resonances in the hammer were detected and examined by modal analysis. A possible influence of the pianist’s touch on the string vibrations via the hammer resonances is discussed.

ISSN:0001-4966    

DOI:10.1121/1.402043

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

The purpose of this study was to examine several factors of vocal quality that might be affected by changes in vocal fold vibratory patterns. Four voice types were examined: modal, vocal fry, falsetto, and breathy. Three categories of analysis techniques were developed to extract source‐related features from speech and electroglottographic (EGG) signals. Four factors were found to be important for characterizing the glottal excitations for the four voice types: the glottal pulse width, the glottal pulse skewness, the abruptness of glottal closure, and the turbulent noise component. The significance of these factors for voice synthesis was studied and a new voice source model that accounted for certain physiological aspects of vocal fold motion was developed and tested using speech synthesis. Perceptual listening tests were conducted to evaluate the auditory effects of the source model parameters upon synthesized speech. The effects of the spectral slope of the source excitation, the shape of the glottal excitation pulse, and the characteristics of the turbulent noise source were considered. Applications for these research results include synthesis of natural sounding speech, synthesis and modeling of vocal disorders, and the development of speaker independent (or adaptive) speech recognition systems.

ISSN:0001-4966    

DOI:10.1121/1.402044

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Hearing threshold levels have been determined in the low‐frequency range (20–500 Hz) on a group of 30 young normal‐hearing subjects using monaural stimulus presentation through an insert earphone (Etymotic Research ER‐3A). A retest was performed on half of the group to provide data on test–retest reliability. The mean hearing threshold levels obtained agree closely with the Minimum Audible Field data of ISO 226, however, with some deviation at the very lowest frequencies below 40 Hz. The test–retest difference results yielded mean values that averaged 1.15 dB with an average standard deviation across test frequencies of 3.9 dB. The results show that low‐frequency hearing thresholds for pure tones of frequencies from 40 Hz and up can be determined with acceptable validity and reliability by the use of this type of insert earphone.

ISSN:0001-4966    

DOI:10.1121/1.402045

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Observations of the otoacoustic emissions (OAEs) evoked during a continuous single stimulus tone have been made on humans using a nonlinear residual time domain technique. The technique, described in this paper, involved the digital summation of responses to contiguous stimulation intervals, some of which included short bursts of a suppressor, or probe, tone. Stimulus intervals are constructed so that both the stimulus and probe tones summed to zero cyclically, leaving a residual response. This residual is attributable to the nonlinearity of the whole acoustic response, as measured in the ear canal, to the stimulus and probe tone complex. A theoretical treatment of this paradigm is presented examining the relation of this residual to the OAE evoked by the stimulus tone. It is shown experimentally that the residual, found at the stimulus tone frequency, has a latency and a saturating input–output growth functions indicative of an OAE. The detailed OAE amplitude‐versus‐frequency variations, and the general latencies of the OAEs in two human ears were measured using both the constant tone evoked residual method described and the click evoked delayed emission method. The results from both methods are in agreement. The frequency‐dependent properties of the suppression of the OAE were investigated using various stimuli to probe frequency ratios. The continuous tone time domain residual method has advantages for the observation of stimulus frequency OAEs and for relating these to any distortion product simultaneously generated.

ISSN:0001-4966    

DOI:10.1121/1.402046

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Single units from the auditory nerve of frogs and toads have their receptor cells located in two separate sensory organs that provide disjoint frequency ranges. The amphibian papilla (ap) provides units with characteristic frequency (CF) in the low‐ and mid‐frequency regions and the basilar papilla (bp) provides units with high CF. There are gross differences in both the mechanical design and innervation patterns of the two organs, so that one might expect discharge properties for units with different CF to differ in many respects. However, there have been few reports of response attributes that correlate strongly with CF for units in the mid‐ and high‐CF regions. Measurements of automated tuning curves from 250 units inRanapipiensshow thatW10dB, the bandwidth of the tuning curve measured 10 dB above CF threshold, is consistently larger for high‐CF units than for low‐ and mid‐frequency units. When units are classified into three groups by an objective statistical method using only CF andW10dBmeasurements, the groups appear to correspond reasonably well with the low‐, mid‐, and high‐frequency categories identified in many other studies.

ISSN:0001-4966    

DOI:10.1121/1.402047

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Human and chinchilla listeners exhibit nonmonotonic temporal acuity for speech sounds differing in voice onset time (VOT). Characteristics of the neural discharge pattern or of the stimuli themselves that might account for the pattern of temporal acuity have not been described. Responses of chinchilla auditory‐nerve fibers to syllables from an alveolar VOT continuum were measured. Peak discharge rates and peak response latencies elicited by the syllables with the shortest and longest VOTs were highly variable across groups of neurons with similar characteristic frequencies. For VOTs from the middle of the continuum, peak responses were larger, and response latencies were nearly constant across the same group of neurons. Overall, the magnitude and temporal variability of the responses of populations of primary auditory neurons varied nonmonotonically with VOT, consistent with the pattern of psychophysical temporal acuity for these syllables exhibited by humans and chinchillas. Spectral analyses suggested by the pattern of neural responses indicated that synchronous or correlated spectral cues were available over a wider bandwidth for those syllables from the middle of the continuum for which the neural representation was least variable.

ISSN:0001-4966    

DOI:10.1121/1.402048

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

This paper describes the temporal responses of anteroventral cochlear nucleus (AVCN) units in the chinchilla to rippled noises. Rippled noise is generated when a wideband noise is delayed and added (cos+ noise) or subtracted (cos− noise) to the undelayed noise. Renewal densities were constructed to evaluate synchronous discharges at the delay. In response to rippled noise, AVCN units which show phase locking to best frequency (BF) tones gave renewal densities having major peaks at the delay for cos+ noise, but nulls at the delay for cos− noise. Most AVCN units which did not show BF phase locking gave renewal densities that did not contain features related to the rippled noise delay; a few of these nonphase‐locked units did show peaks in renewal densities for both cos+ and cos− noises. Synchrony at the rippled noise delay was also demonstrated with evoked potential recording. Autocorrelation functions of the neurophonic potential showed peaks at the rippled noise delay for both cos+ and cos− noises. In addition, peaks could be observed in the autocorrelation functions of neurophonic potentials for rippled noises with delays as short as 1 ms; peaks were never observed in renewal densities of single units for ripple delays as short as 1 ms. The results show that a temporal representation of rippled noise delay does exist in the AVCN and are consistent with current hypotheses regarding functions of AVCN subsystems. The temporal representation of the delay is a presumptive neural code for the pitches of rippled noises.

ISSN:0001-4966    

DOI:10.1121/1.402049

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

Steady‐state evoked potential responses were measured to binaural amplitude‐modulated (AM) and combined amplitude‐ and frequency‐modulated (AM/FM) tones. For awake subjects, AM/FM tones produced larger amplitude responses than did AM tones. Awake and sleeping responses to 30‐dB HL AM/FM tones were compared. Response amplitudes were lower during sleep and the extent to which they differed from awake amplitudes was dependent on both carrier and modulation frequencies. Background EEG noise at the stimulus modulation frequency was also reduced during sleep and varied with modulation frequency. A detection efficiency function was used to indicate the modulation frequencies likely to be most suitable for electrical estimation of behavioral threshold. In awake subjects, for all carrier frequencies tested, detection efficiency was highest at a modulation frequency of 45 Hz. In sleeping subjects, the modulation frequency regions of highest efficiency varied with carrier frequency. For carrier frequencies of 250 Hz, 500 Hz, and 1 kHz, the highest efficiencies were found in two modulation frequency regions centered on 45 and 90 Hz. For 2 and 4 kHz, the highest efficiencies were at modulation frequencies above 70 Hz. Sleep stage affected both response amplitude and background EEG noise in a manner that depended on modulation frequency. The results of this study suggest that, for sleeping subjects, modulation frequencies above 70 Hz may be best when using steady‐state potentials for hearing threshold estimation.

ISSN:0001-4966    

DOI:10.1121/1.402050

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

The estimation of arbitrary time delays in multichannel, multievent systems is studied using a new method called the focus measurement technique (FMT). The method introduced uses the window concept to isolate segments of the data record. However, instead of calculating the generalized cross correlation to estimate delays between data segments, the FMT (based on the assumption of normal distribution) combines windowed‐segment points of every two channels to obtain the focal length of an ellipse which contains a certain amount of these distributed points. Based on simple geometric analysis, the FMT utilizes a windowed‐segment distribution in order to estimate the event delays in the system. Simulation results show that this technique can find delays very accurately down to a signal‐to‐noise ratio (SNR=mean‐square value of signal/mean‐square value of noise) of 0 dB while reducing the amount of computation involved.

ISSN:0001-4966    

DOI:10.1121/1.402051

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP

摘要:

A method of source localization in shallow water, based on subspace concept, is described. It is shown that a vector representing the source in the image space spanned by the direction vectors of the source images is orthogonal to the noise eigenspace of the covariance matrix. Computer simulation has shown that a horizontal array of eight sensors can accurately localize one or more uncorrelated sources in shallow water dominated by multipath propagation.

ISSN:0001-4966    

DOI:10.1121/1.402052

出版商:Acoustical Society of America    

年代:1991

数据来源: AIP