Showing papers on "Noise published in 1991"

Noise exposure from leisure activities : a review

Abstract: Over the past two decades there has been increasing concern about the role of nonoccupational, or leisure noise on hearing. This paper reviews published studies that detail the noise levels and potential effects of some noisy leisure activities. Considered are the most common sources of leisure noise: exposure to live or amplified rock, classical, or jazz music; exposures from personal listening devices (‘‘walkman’’ type); noise around the home, and hunting and target shooting. Although all activities listed above have the potential for dangerous levels of noise exposure, the most serious threat to hearing comes from recreational hunting or target shooting.

Dynamic processes in the precedence effect

Abstract: Three experiments were conducted to investigate the dependence of echo suppression on the auditory stimulation just prior to a test stimulus. Subjects sat in an anechoic chamber between two loudspeakers, one which presented the ‘‘lead’’ sound, and the other the delayed ‘‘lag’’ sound. In the first experiment, subjects reported whether or not they heard an echo coming from the vicinity of the lag loudspeaker during a test click pair. In seven of nine listeners, perception of the lagging sound was strongly diminished by the presence of a train of ‘‘conditioning’’ clicks presented just before the test click. Echo threshold increased (subjects were less sensitive to echoes) as the number of clicks in the train increased from 3 to 17. For a fixed number of clicks, the effect was essentially independent of click rate (from 1/s through 50/s) and duration of the train (from 0.5 through 8 s). A second experiment demonstrated a similar buildup of echo suppression with white noise bursts, regardless of whether the bursts in the conditioning train were repeated samples of frozen noise, or were independent samples of noise. Using an objective procedure for measuring echo threshold, the third experiment demonstrated that both lead and lag stimuli must be presented during the conditioning train in order to produce the buildup of suppression. When only the lead sound was presented during the conditioning train, the perceptibility of the lag sound during the test burst appeared to be enhanced.

Speech enhancement based conceptually on auditory evidence

Abstract: A new idea, enhancing speech based on auditory evidence, is explored for the problem of enhancing speech degraded by stationary and nonstationary additive white noise. Distinguishing different objectives for heavy and light noise interference, two related algorithms are developed. For speech degraded by heavy noise, the improvement in signal-to-noise ratio (SNR) is as high as 12 dB; for lightly noisy speech, the improvement is modest and decreases as the SNR of the noisy speech increases. Quantizing noise is used to assess the capacity for reducing nonstationary noise using these algorithms; a significant reduction of such noise and an improvement in speech quality are achieved. The advantages of the proposed algorithms for speech enhancement include no need for prior knowledge of the noise and only a modest computational requirement. >

Central, auditory mechanisms of perceptual compensation for spectral-envelope distortion.

Abstract: The spectral envelope is a major determinant of the perceptual identity of many classes of sound including speech. When sounds are transmitted from the source to the listener, the spectral envelope is invariably and diversely distorted, by factors such as room reverberation. Perceptual compensation for spectral‐envelope distortion was investigated here. Carrier sounds were distorted by spectral envelope difference filters whose frequency response is the spectral envelope of one vowel minus the spectral envelope of another. The filter /i/ minus /q/ and its inverse were used. Subjects identified a test sound that followed the carrier. The test sound was drawn from an an /itch/ to /qtch/ continuum. Perceptual compensation produces a phoneme boundary difference between /i/ minus /q/ and its inverse. Carriers were the phrase ‘‘the next word is’’ spoken by the same (male) speaker as the test sounds, signal‐correlated noise derived from this phrase, the same phrase spoken by a female speaker, male and female versions played backwards, and a repeated end‐point vowel. The carrier and test were presented to the same ear, to different ears, and from different apparent directions (by varying interaural time delay). The results show that compensation is unlike peripheral phenomena, such as adaptation, and unlike phonetic perceptual phenomena. The evidence favors a central, auditory mechanism.

Sources of auditory masking in infants: distraction effects.

Abstract: Previous work has demonstrated that infants' thresholds for a pure tone are elevated by a masker more than would be predicted from their critical bandwidths. The present studies explored the nature of this additional masking. In Experiment 1, detection thresholds of 6-month-old infants and of adults for a 1-kHz tone were estimated under three conditions: in quiet, in the presence of a 4- to 10-kHz bandpass noise at 40 dB SPL, and in the presence of the same noise at 50 dB SPL. The noise was gated on at the beginning of each trial. Adult thresholds were the same in all three conditions, indicating that little or no sensory masking took place in the presence of the noise. Infant thresholds were about 10 dB higher in the presence of the noise. We term this effect distraction masking. In Experiment 2, the effect of gating the noise on at trial onset was examined. Thresholds for the same tone were estimated in quiet and in the presence of the band-pass noise at 40 dB SPL, but the noise was presented continuously during the session. Under these conditions, distraction masking was still observed for infants. These findings suggest that a masker can have nonsensory effects on infants' performance in a psychoacoustic task.

Quantizing error reducer for audio signal

Abstract: There is provided a quantizing error reducer for an audio signal, which is constructed to feed a quantizing error back to the input side of a quantizer through a noise filter, wherein the coefficient of the noise filter is set on the basis of information relating to the equiloudness curve, thereby making it possible to reduce the noise in the hearing sense.

Vehicle sound system

Abstract: A sound system for a vehicle detects the amount of noise, such as road noise, and automatically controls the audio volume in accordance with the noise amount. There are provided a plurality of tables, in which the relationships among the present volume, the noise amount and the volume increase amount of the audio signal are stored. Once one of the plurality of tables is selected by using a table selection key according to the type of the vehicle or the sound system, the volume is automatically controlled based on the characteristic of the selected table.

Speech detection apparatus not affected by input energy or background noise levels

Abstract: A speech detection apparatus capable of reliably detecting speech segments in audio signals regardless of the levels of input audio signals and background noises. In the apparatus, a parameter of input audio signals is calculated frame by frame, and then compared with a threshold in order to judge each input frame as one of a speech segment and a noise segment, while the parameters of the input frames judged as the noise segments are stored in the buffer and the threshold is updated according to the parameters stored in the buffer. The apparatus may utilize a transformed parameter obtained from the parameter, in which the difference between speech and noise is emphasized, and noise standard patterns are constructed from the parameters of the input frames pre-estimated as noise segments.

Reduced noise interference during handoff

Abstract: A radiotelephone system reduces noise interference during handoff by muting the audio path of a receiver employed in a target base-station (135). After receive a handoff request message, a target base-station (135) mutes the target audio path and determines if the target audio path had been enabled by an undesired interfering signal having a common SAT. If the target audio path had been enabled by a interfering signal having a common SAT, the target base-station (135) will use the SAT and the received signal strength indication (RSSI) of the desired transmission of the subscriber (125) to enable the target audio path. Once the SAT and RSSI are present and adequate, the target audio path is enabled, the source audio path is coupled to the target audio path, and the subscriber (125) is handed off from the source base-station (130) to the target base-station (135) without a third party experiencing an objectionable noise blast.

Spectral sharpening for speech enhancement/noise reduction

Abstract: A spectral sharpening process suitable for speech enhancement and noise reduction is presented. The speech enhancement feature is an efficient precompensation technique for the reduced frequency selectivity encountered among many hearing impaired people. The noise reduction scheme has wider applications. A particular characteristic of the approach is its virtually delayless performance and its structure which easily lends itself to integration. >

Cardiovascular responses and electroencephalogram disturbances to intermittent noises: effects of nocturnal heat and daytime exposure.

Abstract: During sleep, in thermoneutral conditions, the noise of a passing vehicle induces a biphasic cardiac response, a transient peripheral vasoconstriction and sleep disturbances. The present study was performed to determine whether or not the physiological responses were modified in a hot environment or after daytime exposure to both heat and noise. Eight young men were exposed to a nocturnal thermoneutral (20 degrees C) or hot (35 degrees C) environment disturbed by traffic noise. During the night, the peak intensities were of 71 dB(A) for trucks, 67 dB(A) for motorbikes and 64 dB(A) for cars. The background noise level (pink noise) was set at 30 dB(A). The noises were randomly distributed at a rate of 9.h-1. Nights were equally preceded by daytime exposure to combined heat and noise or to no disturbance. During the day, the noises as well as the background noise levels were increased by 15 dB(A) and the rate was 48.h-1. Electroencephalogram (EEG) measures of sleep, electrocardiograms and finger pulse amplitudes were continuously recorded. Regardless of the day condition, when compared with undisturbed nights, the nocturnal increase in the level of heart rate induced by heat exposure disappeared when noise was added. Percentages, delays, magnitudes and costs of cardiac and vascular responses as well as EEG events such as transient activation phases (TAP) due to noise were not affected by nocturnal thermal load or by the preceding daytime exposure to disturbances.(ABSTRACT TRUNCATED AT 250 WORDS)

Reducing audible noise in stereo receiving

Abstract: A receiver for receiving a stereophonic signal with upper and lower sidebands carrying a modulating signal includes independent sideband circuitry for providing upper and lower sideband signals. Selector circuitry responds to the level of audible noise in each of the upper and lower sideband signals for selecting that one of the sideband signals having a lower level of audible noise relative to the other. An ISB highpass filter filters the latter sideband signal to provide a highpass filtered sideband signal. Stereo detector circuitry provides left and right stereophonic audio signals. At least one audio lowpass filter filters the left and right stereophonic signals to provide corresponding lowpass filtered left and right stereophonic audio signals. At least one signal combiner combines the highpass filtered sideband signal with each of the lowpass filtered left and right stereophonic audio signals to provide corresponding composite left and right audio signals.

Speech detection apparatus with influence of input level and noise reduced

Abstract: A speech detection apparatus capable of reliably detecting speech segments in audio signals regardless of the levels of the input audio signals and the background noises. In the apparatus, a parameter of input audio signals is calculated frame by frame, and then compared with a threshold in order to judge each input frame as one of a speech segment and a noise segment, while the parameters of the input frames which are judged as the noise segments are stored in the buffer (109) and the threshold is updated according to the parameters stored in the buffer. The apparatus may utilize a transformed parameter obtained from the parameter, in which a difference between speech and noise is emphasized, and noise standard patterns constructed from the parameters of the input frames pre-estimated as noise segments.

Spectral Character, Exposure Levels and Adverse Effects of Ventilation Noise in Offices:

Abstract: Ventilation noise in offices and related annoyance and other adverse effects were studied in four workplaces, representing high and low levels of ventilation noise. The infrasonic part of the venti...

Noise canceling system

Abstract: PURPOSE:To stop the noise canceling operation when the noise is so small as to be masked by the audio sound. CONSTITUTION:The signal according to the noise generated from a noise source is received as a reference signal SN and a synthesized signal of the noise SN at a noise canceling point and a canceling sound SC is received as an error signal Er by a noise canceling controller 21. A noise canceling signal NC is outputted so that the error signal may be minimized, and a comparative part 28 makes a comparison between an audio signal AS' outputted by an audio circuit 11 and the noise canceling signal N,, and a stopping order SPC of the noise canceling processing is outputted to the noise canceling controller 21 when the audio sound is so large as mask the noise, while an order of continuation and restarting of the noise canceling processing is made when masking can not be made.

Development of an annoyance model based upon elementary auditory sensations for steady-state aircraft interior noise containing tonal components

Abstract: The purpose of this investigation was to develop a noise annoyance model, superior to those already in use, for evaluating passenger response to sounds containing tonal components which may be heard within current and future commercial aircraft. The sound spectra investigated ranged from those being experienced by passengers on board turbofan powered aircraft now in service to those cabin noise spectra passengers may experience within advanced propeller-driven aircraft of the future. A total of 240 sounds were tested in this experiment. Sixty-six of these 240 sounds were steady state, while the other 174 varied temporally due to tonal beating. Here, the entire experiment is described, but the analysis is limited to those responses elicited by the 66 steady-state sounds.

Selective hearing in the aged with regard to speech perception in quiet and in noise. Discussion

Abstract: Most listening environments contain some noise which is mixed up with the speech. The effects of noise on speech perception depend on the parameters of the noise (long term spectrum, fluctuations of the intensity in time and average intensity relative to the intensity of speech) and on the speech material (sentences, monosyllables, CV-, CVC-, VC-syllables). The most effective at masking are noises with spectra similar to the speech spectrum, such as the speech simulating noise (CCITT-noise) or cocktail-party-noise. The cocktail-party situation is judged to be a difficult communication situation not only by the hearing impaired but also by patients with presbycusis. We examined different age-dependent changes of the speech discrimination in noise ability. Using sentences and CV-syllables (rhyme test) the critical signal-to-noise ratios (S/N-dB) for a speech discrimination of 35%-45% were investigated for monaural and binaural noise representations for different age groups. The results are compared to several types of hearing loss and to those of similar studies in literature. The data of this study prove that hearing impaired and elderly patients are greatly affected by noise. While younger patients with moderate high-tone hearing loss may profit from a special hearing aid device with an integrated noise suppression-system, an improvement of speech discrimination in noise for the elderly can be achieved only by enhancing the signal-to-noise ratio by more than 10 dB. This is possibly because of the reduced capacity for frequency-, intensity- and time-resolution in the peripheral and central pathways of the hearing organ of the aged.

The measurement of signal to noise ratio of a television broadcast picture

Abstract: The authors present a method by which an estimate of the signal-to-noise ratio of a television broadcast picture can be made using excursions from the mean signal level in both the horizontal and vertical directions. The method depends on a determination of the two-dimensional spectral components of the noise and can yield nonintrusive measurements during normal broadcasts. In addition, the method can be used on pictures with no areas of constant luminance. The results obtained are consistent with those produced by an industry standard instrument. >

Behavioral and Physiological Responses of Horses to Simulated Aircraft Noise.

Abstract: : The effects of simulated F-4 aircraft noise on pregnancy outcome, behavior, rate of habituation, cardiac function, serum cortisol and progestogen concentrations of pregnant mares were determined. Eight experimental and 8 control mares were exposed to aircraft noise on days 320, 323, and 324 of pregnancy. The noise was heard over 47 sec with sound intensity increasing at 54.7 dB/sec to a maximum of 115 dB. Behavior was viewed using closed circuit TV and tapes were scored by a 5-member panel. All treatment mares delivered live, normal foals without assistance. Mean anxiety and movement scores were significantly different. Heart rate increased during noise periods, but without ectopic arrhythmias. Researchers observed some adaptation to the noise with less of a heart rate increase after successive episodes. Treatment mares experienced a significant rise in serum cortisol only after the first exposure to noise. Progesterone concentrations in serum varied greatly among individuals, but profiles were well within the normal range.

Recording method for id signal

Abstract: PURPOSE:To record an ID signal with less delay by sharing not only a first level but also a second level smaller than the first level as previously decided levels. CONSTITUTION:A detected recording level L is judged to be in a first state where it is smaller than the previously decided first level L1 or in a second state where the level L is smaller than the second level L2. When either of the first state or the second state continues for prescribed time, start ID are recorded by setting that the recording level L comes more than the first level L1 as a trigger after the first state continues and that the recording level L comes more than the second level L2 as the trigger after the second state continues. Thus, recording without delay is attained by securely adjusting start ID to the starting point of music for recording start ID when recording is executed from recording sources different in noise levels.

Connecting cable for audio equipment

Abstract: PURPOSE: To control flow of a noise current unnecessary for an earth cable housed in an audio equipment by improving a cable for connecting audio equipments to each other. CONSTITUTION: A two-core shield cable 1 for a right channel is twisted together with a two-core shield cable 2 for a left channel. Consequently, it is possible to cancel an effect of an electromagnetic field from the exterior in an earth cable loop, which is generated in connecting audio equipment, and control a flow of a noise current unnecessary for an earth cable housed in the audio equipment. COPYRIGHT: (C)1993,JPO&Japio

Sound field effect automatic controller

Abstract: PURPOSE:To eliminate noise due to changeover between an audio part and a musical sound part by mixing two signals in stereo transmission and a differential signal and outputting the mixed signals so that the mixture ratio is changed complimentarily in response to the lapse of time from a point of time when the audio part and the musical sound part of an audio signal are switched. CONSTITUTION:A differential signal generating circuit 15 outputs a difference (c) between two signals a, b in stereo transmission in audio signals of plural channels. A mixing circuit 21 mixes the two signals a, b and the output (c) from the differential signal generating circuit 15 and outputs the result so that the mixture ratio is changed complimentarily in response to the lapse of time from a point of time of changeover of the result of decision outputted from a decision means 19 deciding the audio part and the musical sound part of an audio signal are switched. Then a sound field effect circuit 17 provides a sound field effect to an output from the mixing circuit 21. Then the mixture rate where the difference signal (c) is mixed in L, R signals changes gradually from a point of time of the changeover of the audio part and the musical sound part thereby preventing generation of noise.

A new noise reduction system for video camera

Abstract: A novel noise reduction system developed to improve the sensitivity of video cameras is reported. The frequency resolution characteristics, feedback characteristics, and bit accuracies of the noise reduction circuit in which the field or frame difference signal is separated into frequency components were studied for improving the S/N (signal-to-noise ratio) of the color difference signal, and for optimizing its circuit construction. An S/N improvement as high as 9 dB at a permissible lagged image level is thus accomplished, and this is to be used to improve the sensitivity of home video cameras. >

Apparatus for muting noise resulting from reproducing of a PCM audio signal recorded in an extension of a slant track containing a recorded video signal

Abstract: An apparatus for reproducing video signals recorded in slant tracks on a magnetic tape also having respective pulse code modulated audio signals recorded in extensions of the slant tracks with gaps therebetween: comprises a rotary head drum having magnetic heads mounted thereon with an angular spacing of 180 degrees therebetween for scanning the slant tracks and extensions thereof and thereby providing reproduced head outputs containing video and audio signals reproduced from the magnetic tape with dropouts in said reproduced head outputs corresponding to the gaps between the respective recorded video and audio signals; and a signal extracting circuit including a head changeover switch receiving the reproduced head outputs and responsive to a head switching signal synchronized with rotation of the head drum to provide a switched output which, in a normal reproducing mode employing a tape speed equal to that for recording, consists of the reproduced video signals and, in another reproducing mode employing a different tape speed, also includes the dropouts and noises corresponding to at least portions of the reproduced audio signals. Dropouts in the switched output are detected to provide dropout detected pulses, and the switched output is muted in response to muting signals each initiated by a respecitve dropout detected pulse and continuing for a period corresponding to the duration of the respective dropout and the following noise so as to eliminate from the switched output in the other reproducing mode noises due to audio signals that may be contained therein.