Showing papers on "Noise published in 1997"

Multi-channel speech enhancement in a car environment using Wiener filtering and spectral subtraction

Abstract: This paper presents a multichannel-algorithm for speech enhancement for hands-free telephone systems in cars. This new algorithm takes advantage of the special noise characteristics in fast driving cars. The incoherence of the noise allows to use adaptive Wiener filtering in the frequencies above a theoretically determined frequency. Below this frequency a smoothed spectral subtraction (SSS) is used to get an improved noise suppression. The algorithm yields better results in noise reduction with significantly less distortions and artificial noise than spectral subtraction or Wiener filtering alone.

Habituation and dishabituation to speech and office noise

Abstract: The authors examined whether background noise can be habituated to in the laboratory by using memory for prose tasks in 3 experiments. Experiment 1 showed that background speech can be habituated to after 20 min exposure and that meaning and repetition had no effect on the degree of habituation seen. Experiment 2 showed that office noise without speech can also be habituated to. Finally, Experiment 3 showed that a 5-min period of quiet, but not a change in voice, was sufficient to partially restore the disruptive effects of the background noise previously habituated to. These results are interpreted in light of current theories regarding the effects of background noise and habituation; practical implications for office planning are discussed.

Sold out on soul: The corporate annexation of black popular music

Abstract: (1997). Sold out on soul: The corporate annexation of black popular music. Popular Music and Society: Vol. 21, Cartographies of Sound, Noise, and Music at Century' End, pp. 117-135.

Environmental noise reduction based on speech/non-speech identification for hearing aids

Abstract: We proposed a very practical and useful noise reduction system that has wide application for hearing impaired persons, such as a sound-gathering system at a lecture hall or conference room. The system uses two basic technologies, a speech/non-speech identification process and a new noise reduction process. A speech/non-speech identification process uses four characteristics of the time and frequency domains of the input signal. In the noise reduction process, frequency weighting function is used for basic spectral subtraction and a loss control algorithm. Various kinds of environmental noise were reduced by this system, which showed excellent performance. Noise is further reduced by using a multi-microphone system as an acoustic noise suppressor. The results of intelligibility tests using persons with hearing loss show excellent noise reduction.

Method and apparatus for automatic tracing of Doppler time-velocity waveform envelope

Abstract: An analytical method for automatic tracing of a Doppler time-velocity waveform envelope. At the core of this algorithm is a maximum frequency detection mechanism which is based on searching for the highest frequency bin whose spectral amplitude exceeds a certain noise threshold. The method is based on a theoretical noise amplitude distribution in the video spectral domain. In particular, the method uses a precise model of the statistical distribution of the video spectral power of white noise to establish a threshold for maximum frequency detection. Input to the noise model is the average white noise level in the video spectral display, which can be computed using either of two analytical methods.

Combining noise compensation with visual information in speech recognition

Abstract: The addition of visual information derived from the speaker’s lip movements to a speech recogniser (speechreading) can signicantly enhance the performance of the recogniser when it is operating under adverse signal-to-noise ratios. However, processing of video signals imposes a large computational demand on the system and there is little point in using speechreading techniques if similar performance gains can be obtained using techniques which operate on only the audio signal and which are less computationally expensive. In this paper, we show that combining visual information with an audio noise compensation technique (spectral subtraction) leads to a performance signicantly higher than that obtained using speechreading only or noise compensation only. The optimum method for speech recognition in the presence of noise is to use speech models that are matched to the input speech, and we show that the addition of visual information also gives a performance gain when matched models are used. We also describe a method of ilatei integration which uses a measure of condence derived from information output by the audio recogniser to achieve a performance which is close to optimum.

Time-scale modification of audio signals with combined harmonic and wavelet representations

Abstract: We propose a new time-scale modification method for high quality audio signals. Our approach strives to preserve pitch and timbre. In our method, the signal is represented as the sum of sinusoidal components and a residual (edges and noise). The decomposition is computed via a combined harmonic and wavelet representation. Time-scaling is performed on the harmonic components and residual components separately. The harmonic portion is time-scaled by demodulating each harmonic component to DC, interpolating and decimating the DC signal, and remodulating each component back to its original frequency. The residual portion is time-scaled by preserving edges and relative distances between the edges while time-scaling the stationary (noise) components between the edges.

Too quiet to hear a whisper

Abstract: Add some noise, and many dynamic systems respond to weak signals more strongly. Some sort of threshold process was thought to be necessary for this effect, but a new model removes the restriction.

Method and arrangement for reproducing audio signals

Abstract: An arrangement for reproducing audio signals includes a pitch control device for increasing or decreasing the amplification of audio signals in one or more defined frequency ranges and a volume control device for increasing and decreasing the amplification of the audio signals in a full effective frequency range of the audio signals wherein the pitch control device reduces the amplification in the defined frequency ranges if the amplification of the audio signals in the full effective frequency range is increased by the volume control device and wherein the pitch control device increases the amplification of the audio signals in the defined frequency ranges if the volume control device decreases the amplification of the audio signals in the full effective frequency range. In order to compensate for noise interference signals which occur and in order to suppress them in the audio signal sound pattern which can be heard by a human being, an additional amplification component is added to the frequency curve in at least one of the defined frequency ranges in which noise interference occurs.

Can't touch this! representations of the African American female body in urban rap videos

Abstract: (1997). Can't touch this! representations of the African American female body in urban rap videos. Popular Music and Society: Vol. 21, Cartographies of Sound, Noise, and Music at Century' End, pp. 107-116.

Spectral amplitude warping (SAW) for noise spectrum shaping in audio coding

Abstract: In this paper, we present a new approach to shape the coding noise in speech and audio coders. The approach, called spectral amplitude warping (SAW), consists essentially of a pre- and post-processing which apply a nonlinear transformation to the signal short-term spectrum prior to, and after, encoding. Since it is possible to view SAW as a separate entity from the coder, the noise shaping capability of an existing coder can be improved without modifying the coder itself. Using SAW as a pre- and post-process to the G.722 wideband speech coding standard, it was found in an informal listening test that the quality of the 64 kb/s operating mode can be achieved at only 48 kb/s. The price to be paid is an additional delay.

Word Recognition in Continuous Noise, Interrupted Noise, and in Quiet by Normal-Hearing Listeners at Two Sensation Levels

Abstract: The effect of presentation level on word recognition performance-intensity functions in continuous and interrupted broadband noise and in quiet was explored. Normal-hearing participants were tested at 30 and 50dB sensation levels (SLs). Performance-intensity functions in both noises were determined at signal-to-noise ratios (S/Ns) of 10. 5. 0. -5. -10, -15, and -20 dB. There was no effect of SL presentation on word recognition performance in quiet (p = 0.136). A significant main effect was observed for S/N in both continuous and interrupted broadband noise conditions (p < 0.0001). Performance increased with increases in S/N regardless of the competing noise condition. A significant main effect for SL presentation was only observed in the interrupted noise condition (p = 0.0019). That is. performance was higher for the 50SL for the interrupted noise condition only. It is suggested that the observed difference in performance in interrupted noise at different SLs offers additional evidence for level-dependen...

Noise: The Invisible Hazard

Abstract: How do we hear? The human ear is composed of three major sec­ tions: the outer, middle and inner ear (see Figure 1). Each section has a specific function in the hearing process. The middle ear consists of three tiny bones, or ossicles, that are suspended in an air-filled space. They connect the eardrum to the inner ear, which is embedded in the skull. The (~<;sicles function as a mechanical lever system that delivers sound from the ear canal to the inner ear. Noise does not affect the middle ear unless there is an impact sound or pres­ sure so great that it dislodges or fractures the ossicles. In the inner ear, the cochlea is susceptible to dam­ age from continued exposure to high-level noise. The cochlea (Latin term meaning snail shell) is a fluid­ filled hydraulic system driven by the piston action of the last ossicle. The vibrating motion of the ossicle produces a wave motion in a membrane that runs the full length of the cochlea. If the vibrations are fast (high-frequency sound), the membrane has its great­ est motion at the base of the cochlea near the vibrat­ ing ossicle. If the vibrations are slow (low-frequency sound), the maximum membrane motion occurs at the tip, or apex, of the cochlea. Situated on top of the moving membrane are thousands of small hairlike structures with nerves connected to each hair cell. When a hair cell is bent because of membrane motion, the nerve fires and the message is transmitted to the brain. Hair cells near the base transmit information about high-frequency, or high-pitched, sound, while those at the apex pro­ vide information about low-pitched sound. If the hair cells in a particular region of the cochlea are destroyed, the nerves will not fire and the brain will not receive any information. If part of the Outer ear Middle ear Inner ear

Methods and devices for noise conditioning signals representative of audio information in compressed and digitized form

Abstract: The present invention relates to methods and devices for processing data frames representative of audio information in digitized and compressed form. The method comprises the steps of classifying succesive data frames into frames containing speech sounds and non-speech sounds, altering parameters of the data frames identified as containing non-speech sounds for eliminating or at least substantially reducing artifacts that distort the acoustic background noise. In addition, the data frame identified as containing non-speech sounds are low-pass filtered. Finally, a signal level compensation is effected to avoid undesired fluctuations in the signal level.

Detrimental Effects of Noise on Anaesthetists

Abstract: To study the detrimental effects of operating room noise, noise levels in operating rooms were first measured and the average noise level was calculated in Decibels, which was 77.32 dB(A). An audiocassette of 90 min duration was prepared recording the operating room noise. The same audiocassette was used later to expose the 20 anaesthesia residents to the operating room noise in the acoustically treated rooms of audiology department. The noise level during exposure was maintained at 77.32 dB(A). Two cognitive functions, mental efficiency and short-term memory were studied. The tests used were the Trail Making Test and Digit Symbol Test for mental efficiency and the Benton Visual Retention Test for short-term memory. The mean pre-exposure scores for the Trail Making Test, Digit Symbol Test and Benton Visual Retention Test were 22.9± 1.94, 83± 2.62 and 9.55± 0.51 respectively. The mean during-exposure scores were 16.35± 1.39, 74.05± 3.46 and 5.8± 0.41 respectively (P < 0.05). In conclusion, we observed that operating room noise reduced the mental efficiency and short-term memory of anaesthesia residents.

Active noise reduction versus conventional hearing protection. Relative benefits for normal-hearing and impaired listeners.

Abstract: The benefits of active noise reduction (ANR) hearing protectors were assessed in two groups of normal-hearing subjects, under and over the age of 40 years, and one group with bilateral high-tone hearing loss. Subjects were tested with the ears unoccluded and fitted with conventional sound attenuating E-A-R foam plugs, E-A-R HI-FI plugs, and Bilsom Viking muffs; and one ANR muff, the Peltor 7004. Within each ear condition, measurements were made in quiet of hearing thresholds for frequencies between 0.25 kHz and 8 kHz, duration and frequency difference limens, and word recognition. Hearing thresholds and word recognition were also measured in a background of impulsive cable swager noise. The E-A-R foam plug provided the highest and the E-A-R HI-FI plug, the lowest attenuation. The Bilsom Viking and Peltor muffs were virtually identical and midway between. An additional 10 dB of sound reduction was realized at 0.25 kHz with ANR. The masking effect of the noise on hearing threshold decreased with an increase in attenuation. None of the devices compromised either duration or frequency discrimination. Word recognition in noise improved in normal listeners when protectors were worn. For the impaired subjects, word recognition with poor contextual cues decreased with an increase in sound attenuation, in both quiet and noise. Like older normal listeners, their scores were relatively higher with ANR.

Perceptual coding of audio signals employing envelope uncertainty

Abstract: Perceptual coding is accomplished by measuring the envelope roughness of the filtered audio signal, which may be directly converted to the noise to mask threshold needed to calculate the perceptual threshold or “just noticeable difference”. Thus, the present invention does not require any complex calculations to determine tonality, either by a measure of predictability or by the calculation of a loudness or loudness uncertainty. Instead, the envelope roughness of the signal is simply reduced directly to the noise to mask ratio.

Method and device for voice processing

Abstract: PROBLEM TO BE SOLVED: To accurately detect a voice interval against an object sound source employing a small number of microphones under the environment in which the S/N ratio is low and the direction to a noise sound source is not specified. SOLUTION: In the device, a voice input section 10 inputs audio signals to terminals 10-1 to 10-n through plural channels ch1 to chn. A beam former processing section 20 conducts a beam former process against the audio signals inputted by the section 10 to suppress the signals arriving from an object sound source. An object sound source direction estimating section 30 obtains the direction to the object sound source from the filter coefficients obtained by the section 20. A voice/non-voice determining section 40 determines the voice interval of the audio signals based on the estimated direction to the object sound source.

A combined approach for broadband noise reduction

Abstract: This paper deals with broadband noise reduction for the restoration of audio recordings. The signals are processed in the frequency domain using the short-time Fourier transform. A method based on non-linear spectral subtraction is presented. To prevent the annoying phenomenon of musical noise which is caused by the noise suppression process, over-subtraction is applied to the degraded signal spectrum. This means that depending on the estimated signal-to-noise ratio (SNR) more than the average noise spectrum is subtracted. A masking threshold obtained by spectral smoothing of the degraded signal spectrum is used to determine the SNR. Furthermore, time-averaging is applied to the SNR. The averaging procedures in the time and frequency domain reduce the SNR variance. Therefore, audible processing distortions are reduced, too.

Weighted matching algorithms and reliability in noise cancelling by spectral subtraction

Abstract: This paper addresses the problem of speech recognition with signals corrupted by additive noise at moderate SNR. A technique based on spectral subtraction and noise cancellation reliability weighting in acoustic pattern matching algorithms is studied. A model for additive noise is proposed and used to compute the variance of the hidden clean signal information and the reliability of the spectral subtraction process. The results presented show that a proper weight on the information provided by static parameters can substantially reduce the error rate.

A consideration of the effect of ear canal resonance and hearing loss upon white noise generators for tinnitus retraining therapy

Abstract: Tinnitus retraining therapy has been heralded as a major advance in the alleviation of tinnitus perception. A cornerstone of this technique is to use white noise produced by a white noise generator (WNG) over a period of several months in order to assist the patient to habituate to their tinnitus. There are three factors which influence the frequency spectrum of the perceived noise such that the perception of white noise from a WNG is unlikely. These factors are the actual spectrum of the emitted noise, the ear canal resonance of the patient and the hearing sensitivity of the patient. Advocates of tinnitus retraining therapy state that white noise is the optimal stimulation to assist habituation of tinnitus. This paper demonstrates that this optimal situation is unlikely to be achieved and that this may account for the long periods needed for patients to achieve benefit from the technique. The development of devices that allow for the above factors to be countered is suggested.

Variable-length moving-average filter

Abstract: A filter for a system for processing audio samples, which dynamically vaires its length responsive to a moving average of variations in an audio input rate. The filter lengthens at substantially constant input rate variations to reduce input noise, and shortens at rapid input rate variations to enhance responsiveness.

Telecommunication apparatus capable of controlling audio output level in response to a background noise

Abstract: A method of detecting a noise level from audio signals produced consecutively in time by a microphone. The method includes the steps of evaluating an average level of the audio signals consecutively in time, and selecting the smallest of the average levels as the noise level. A telecommunication apparatus for adaptively controlling an audio output level in response to the noise level thus detected is also disclosed.

Music marketing: Tropes of hybrids, crossovers, and cultural dialogue through music

Abstract: (1997). Music marketing: Tropes of hybrids, crossovers, and cultural dialogue through music. Popular Music and Society: Vol. 21, Cartographies of Sound, Noise, and Music at Century' End, pp. 61-82.

Noise cancelling for microphone arrays

Abstract: An application of the noise cancelling method for suppression of noise of a microphone array system is discussed. First an overview of the noise cancelling approach is given. This is followed by a description of the employment of the method in a realized microphone array system. The limiting factors are described and theoretical limits of the noise suppression are derived. Experimental results, which are obtained in a realistic environment, are presented. The results show that depending on the recording situation the noise cancelling approach applied to a microphone array system leads to a significant enhancement of the signal to noise ratio of the array output signal.

Noise analysis of three newborn infant isolettes.

Abstract: OBJECTIVE The purpose of this study was to evaluate the noise of three newborn infant isolettes. STUDY DESIGN An observational, prospective study evaluated noise in three isolettes (Ohmeda, Air Shields, and Drager). The study measured interior isolette noise production during quiet noise situations and isolette noise attenuation of added low- and high-frequency noise. Noise was measured on the decibel A scale and in the 125 Hz and 1000 Hz bands. RESULTS During quiet conditions the Ohmeda and Drager isolettes had the least noise production on the basis of decibel A levels (p < 0.001). Low-frequency noise on the decibel A scale was attenuated the most by the Drager isolette (p < 0.001), although the overall difference may be clinically insignificant. The Ohmeda isolette attenuated high-frequency noise by 28.4 dB as measured on the decibel A scale, which was greater than values for the Drager (22.8 dB) and Air Shields (14 dB) isolettes (p < 0.001). CONCLUSIONS High-frequency noise attenuation by the Ohmeda and Drager isolettes is clinically and statistically greater than high-frequency noise attenuation by the Air Shields isolette.