Showing papers on "Noise published in 1985"

Effects of room reverberation and noise on speech discrimination by the elderly.

Abstract: Speech discrimination performance was measured in sound field for 10 young normal-hearing subjects, 10 elderly ‘normal-hearing’ subjects with a mean pure-tone average of 9.9 dB HTL, and 10 elderly hearing-impaired subjects with a mean pure-tone average of 48.5 dB HTL. Speech discrimination abilities were assessed in quiet and noise (S/N = +10 dB) in a sound suite and under two levels of reverberation in a reverberant room (RT = 0.59 and 1.56 s). Results indicated that the elderly ‘normal-hearing’ and young normal-hearing subjects have similar speech discrimination performance in the sound suite for both the quiet and noise conditions. In addition, performance by these two groups was almost identical under both levels of reverberation in quiet. However, when noise was added to the reverberant conditions, performance by the elderly ‘normal-hearing’ subjects was significantly poorer than that obtained by the young normal-hearing subjects. The elderly hearing-impaired subjects yielded speech discrimination sc...

Some acoustic-phonetic correlates of speech produced in noise

Abstract: Acoustical analyses were carried out on the digits 0-9 spoken by two male talkers in the quiet and in 90 dB SPL of masking noise in their headphones. The results replicated previous studies demonstrating reliable increases in amplitude, duration and vocal pitch while talking in noise. We also found reliable differences in the tilt of the short-term spectrum of consonants and vowels. The results are discussed in terms of: (1) the development of algorithms for recognition of speech in noise; (2) the nature of the acoustic changes that take place when talkers produce speech under adverse conditions such as noise, stress or high cognitive load; and, (3) the role of training and feedback in controlling and modifying a talker's speech to improve performance of current speech recognizers.

Vowel errors in noise and in reverberation by hearing‐impaired listeners

Abstract: The effects of noise and reverberation on the identification of monophthongs and diphthongs were evaluated for ten subjects with moderate sensorineural hearing losses. Stimuli were 15 English vowels spoken in a /b–t/ context, in a carrier sentence. The original tape was recorded without reverberation, in a quiet condition. This test tape was degraded either by recording in a room with reverberation time of 1.2 s, or by adding a babble of 12 voices at a speech‐to‐noise ratio of 0 dB. Both types of degradation caused statistically significant reductions of mean identification scores as compared to the quiet condition. Although the mean identification scores for the noise and reverberant conditions were not significantly different, the patterns of errors for these two conditions were different. Errors for monophthongs in reverberation but not in noise seemed to be related to an overestimation of vowel duration, and there was a tendency to weight the formant frequencies differently in the reverberation and quiet conditions. Errors for monophthongs in noise seemed to be related to spectral proximity of formant frequencies for confused pairs. For the diphthongs in both noise and reverberation, there was a tendency to judge a diphthong as the beginning monophthong. This may have been due to temporal smearing in the reverberation condition, and to a higher masked threshold for changing compared to stationary formant frequencies in the noise condition.

Some experimental and theoretical results using a new adaptive filter structure for noise cancellation in the presence of crosstalk

Abstract: The application of adaptive filters in noise cancelling often requires the relative placement of the two transducers at a distance that necessitates a large order filter in order to obtain an adequate output signal-to-noise ratio. A new adaptive filter structure is introduced that permits a closer placement of the transducers and that allows the cancellation of noise in the presence of crosstalk. Algorithms are developed for the new transversal and lattice structures. Simulations show considerable improvement in mean-square error over that obtained with standard noise cancelling algorithms.

Signal Detection in Industrial Noise: Effects of Noise Exposure History, Hearing Loss, and the Use of Ear Protection

Abstract: The detection of one-third octave signals superimposed on backgrounds of steady-state and intermittent industrial noise of 84 dBA was investigated for observers with normal hearing or moderate to severe noise-induced hearing loss (NIHL). Variables included age, noise exposure history, configuration of the audiogram and the wearing of insert hearing protectors. Detection thresholds were obtained binaurally over headphones using a two- interval forced-choice procedure. For unprotected listening all observers showed a masked threshold of about 80 dBA for a one-third octave band cented at 3.15 kHz. Neither variation in noise exposure history nor configuration of the audiogram were significant factors. Using insert protectors in noise, observers with normal hearing showed an advantage on average of 3 dB. Those with NIHL gave masked detection thresholds greater than 100 dBA. Detection of a one-third octave band centred at 1 kHz by hearing-impaired observers with mild to moderate loss at 1 kHz was similar to that for normal observers. A model of the detection process was developed and evaluated.

Loudness assessment of band noise of varying band-width and spectral shape. An evaluation of various frequency weighting networks

Abstract: The ability of different evaluation methods to predict loudness was assessed. In Experiment I, 12 subjects matched a band noise (900–1060Hz) to equal the loudness of each of 45 different noises covering the 15–1060 Hz frequency range, cut from three band spectra: Spectrum ‘STRAIGHT’ had its energy evenly distributed across frequency, ‘INVERSE’ was unbalanced towards the low-frequency bands and ‘A’ was unbalanced towards the high. Six frequency weighting networks: dB(A), dB(B), dB(C), dB(D), PLdB and PhondB were assessed. dB(B) fared best, followed by dB(D)and PhondB. dB(A) underestimated an dB(C) overestimated loudness especially when the noise only contained lower frequency bands. In Experiment II, 12 subjects matched the loudness of 7 noises cut from power spectrum ‘STRAIGHT’ at three different levels, all containing the 15–100 Hz low-frequency band. PLdB and PhondB predicted loudness best, followed by dB(D) and dB(B). Level proved to be of minor importance. In neither experiment did dB(A) predict the loudness of any noise better than dB(B) or dB(D).

The effects of multitalker and masker noise on fundamental frequency variability during spontaneous speech for children and adults.

Abstract: Young adults (N:10) and children aged 5-10 yrs (14 M, 14 F) spoke spontaneously in quiet and in the presence of masking at 90 db SPL in binaural earphones, either white noise or multitalker noise. Fundamental frequency (fo) variability data (coefficients of variation) for the stressed and nonstressed words were submitted to ANOVA. Fo variability observed during the production of stressed words was significantly more variable than nonstressed words. Also, multitalker noise affected performance variability while white noise did not. Evidence supporting the operation of a mixed control strategy during speech production was discussed.

Comparison of speech recognition-in-noise and subjective communication assessment.

Abstract: A comparison was made between speech recognition performance in conditions of quiet and babble (Speech Perception in Noise Test) and items from a self-assessment scale concerned with communication ability in quiet and noise (Understanding Speech section of Hearing Performance Inventory). Performance on both the speech recognition and self-assessment tests differentiated between normal listeners and individuals with mild-to-moderate sensorineural hearing loss. For the hearing-impaired group, correlations between speech recognition scores and ratings on the self-assessment items were poor, suggesting that performance measured with these tests have only a weak relationship.

The effect of signal degradation on the status of cues to voicing in utterance‐final stop consonants

Abstract: In several recent studies, spectral acoustic cues (eg, voicing during closure, preclosure transition) have been found to have more influence than temporal acoustic cues (eg, vowel or syllable duration) on perception of the voicing distinction in final stops Earlier studies, mostly using synthetic speech, had found vowel duration to be the primary cue to this distinction The present stimuli were taken from a study in which spectral cues had dominated judgments in quiet listening conditions These stimuli were presented against a high level of background noise (S/N=0) to seven normal adult subjects in a forced choice (eg, BED–BET) format In quiet, the correlation of the percentage of the original vowel remaining after deletion with judgments of the final stop as voiced had been 018 In the noise listening condition the correlation was 094 Syllables with voiced final stops from which 76% of the vowel (all but the final transition) had been deleted were judged voiced (82%) in quiet but voiceless (87%) in noise These results indicate that the temporal cue of vowel duration is more resistant to degradation by noise than are spectral cues, and that vowel duration plays a dominant role only when other cues are unavailable

Penalty for impulse noise, derived from annoyance ratings for impulse and road-traffic sounds.

Abstract: In the laboratory, four groups of 16 subjects rated the annoyance caused by three types of impulse sounds (regular and irregular gunfire noise and metal‐construction noise) and by road‐traffic sounds, all presented in background noise. The subjects were presented with the sounds for 5‐min periods. The annoyance ratings were related to the A‐weighted equivalent level (Leq) of the sounds. From these annoyance ratings a correction term or penalty was derived, which, added to the Leq of the impulse sounds, gives the level of equally annoying traffic noise. The correction was determined for conditions in which (1) only the annoyance caused by specific sources, or (2) the annoyance caused by the total sound (specific source plus background) had to be rated. In addition, the indoor Leq of the constantly present background noise was 35 or 55 dB(A) by and large, the results showed that for lower levels of the sounds an impulse‐noise correction of at least 10 dB was required, whereas for higher levels the derived c...

Contribution of tonal components to the overall loudness, annoyance and noisiness of noise: Relation between single tones and noise spectral shape

Abstract: A large scale laboratory investigation of loudness, annoyance, and noisiness produced by single-tone-noise complexes was undertaken to establish a broader data base for quanitification and prediction of perceived annoyance of sounds containing tonal components. Loudness, annoyance, and noisiness were distinguished as separate, distinct, attributes of sound. Three different spectral patterns of broadband noise with and without added tones were studied: broadband-flat, low-pass, and high-pass. Judgments were obtained by absolute magnitude estimation supplement by loudness matching. The data were examined and evaluated to determine the potential effects of (1) the overall sound pressure level (SPL) of the noise-tone complex, (2) tone SPL, (3) noise SPL, (4) tone-to-noise ratio, (5) the frequency of the added tone, (6) noise spectral shape, and (7) subjective attribute judged on absolute magnitude of annoyance. Results showed that, in contrast to noisiness, loudness and annoyance growth behavior depends on the relationship between the frequency of the added tone and the spectral shape of the noise. The close correspondence between the frequency of the added tone and the spectral shape of the noise. The close correspondence between loundness and annoyance suggests that, to better understand perceived annoyance of sound mixtures, it is necessary to relate the results to basic auditory mechanisms governing loudness and masking.

Speech recognition and manner of speaking in noise and in quiet

Abstract: Currently speech recognition is accomplished by matching spoken utterances with reference patterns of words that were spoken by an individual at an earlier time. Recognition is highly dependent upon background noise. The purpose of this study was to assess the extent to which subjects “manner” of speaking in noise, as separate from the noise itself, affected recognition. Subjects generated reference patterns in quiet and in noise and then spoke lists of digits in quiet and in noise for the speech system to recognize. Noise was delivered over earphones so it would not go into the speech recognition system through the microphone. Training and recognition were done from tape recordings, with the playback level of the tape was always set to the same, intermediate level. The data suggest that manner of speaking, for about half of the subjects is very different in noise compared with quiet. The data also imply that if recognition will be done in both quiet and noise, the safest alternative is to start out with patterns generated in noise.

Quiet centrifugal fan

Abstract: A fan is disclosed that contains cut-outs that reduce the noise levels. The fan is used to cool circuit boards.

A biological chorus in deep water northwest of Australia

Abstract: This paper is a summary of observations of a biological chorus in deep waters northwest of Australia. The data were collected from underwater noise recordings made in the course of sonar performance trials at sites in the eastern Indian Ocean. Measurements are made for frequencies between 20 and 800 Hz. Chorus noise at 500 Hz, consisting of continual drumming sounds, was evident for 9–10 h in the evening, with the peak noise level occurring soon after sunset. The noise spectrum level at this peak frequency rose to 72 dB re: 1 μPa2/Hz, approximately 12 dB above the background noise level. Typical spectra and time waveforms for individual noise bursts are presented. The source of the noise is believed to be fish of the family Sciaenidae, commonly known as croakers.

Adaptive noise reduction in aircraft communication systems

Abstract: It has been reported that the application of broadband noise cancelling techniques to the control of aircraft cockpit noise pickup is only successful at low frequencies This effect is explained in terms of measures of the noise transmission across a standard British oxygen mask and a discussion of the spatial characteristics of the cockpit's acoustic field A theoretical prediction of the maximum noise reduction given by a single channel noise cancelling system controlling a group of independantly excited noise transmission paths is presented

Eliminating undesirable noise recordation in image sensing/sound recording device

Abstract: An image sensing device includes a voltage converting device for supplying power for driving a peripheral equipment component such as a flash unit used with the image sensing device, a recording device for recording an audio signal and a control device for prohibiting simultaneous operation of the voltage converting device and the recording device. The control device has a control mode in which both the peripheral equipment and the recording device are used at the time of photography. The control device also has a control mode in which the peripheral equipment is operated in preference to the recording devide. Accordingly, the mixture of noise from the voltage converting device with the audio recording signal is prevented.

Effects of noise on NST and NU 6 stimuli.

Abstract: This study determined how normal-hearing listeners' performance on a nonsense syllable test (NST) was affected by three noise competitors, and how these responses differed from those on the standard NU 6 meaningful word test. Twenty young adult listeners heard the stimuli via earphones and provided verbal responses to the NST and NU 6 items in competition with: white noise, multitalker noise, and white noise which was amplitude modulated by the multitalker noise, each at a 0 dB signal-to-noise ratio. Responses were scored on a whole-word (all-or-none) basis. Statistical analyses revealed that listeners' performance was always poorer on the NST than on the NU 6 regardless of competitor type; and that scores were better in the multitalker noise followed by white noise and amplitude modulated white noise. These data and those from earlier studies indicate that the NST is sufficiently difficult in quiet that it may not warrant testing in noise.

Auditory Distance Judgments in Noise, with and without Hearing Protection:

Abstract: Previous studies of the effects of hearing protective devices (HPDs) on auditory localization have all been concerned with directional judgments. The present study examined the influence of such devices upon judgments of distance under conditions of noise. Blindfolded observers were required to verbally report the apparent distance to a target sound under one of three conditions: quiet (60 dBA), noise (90 dBA) or noise (90 dBA) while wearing inserted foam plugs. Judgments in quiet were found to be reasonably correct. The presence of high-level noise, however, decreased the judged distances significantly. The use of the HPD neither improved these latter judgments, nor did it produce any further error. The findings are fully consistent with present understanding of the bases for auditory distance perception.

Effects of changes in absolute signal level on psychophysical tuning curves in quiet and noise in patas monkeys

Abstract: Forward masking psychophysical tuning curves (PTCs) were measured in patas monkeys (Erythrocebus patas) at 2, 4, and 8 kHz at signal levels of 10, 30, and 60 dB SL in quiet, and at 10 dB above masked threshold in two levels of wideband noise. Absolute signal levels with masking approximated those at 30 and 60 dB SL in quiet. Results in quiet agree with those reported in the literature, demonstrating broadening of the PTC as signal level is increased. The PTCs measured in noise also demonstrated a similar broadening, or loss of selectivity, at higher SPLs. These later findings differ from those of a previous study [D. M. Green, B. R. Shelton, M. C. Picardi, and E. R. Hafter, J. Acoust. Soc. Am. 69, 1758–1762 (1981)] which used maskers to control the broadened excitation pattern in humans at levels of up to 34 dB above threshold. Differences in findings might be attributed to higher SPLs used in the present study. The data taken in noise backgrounds are not consistent with explanations for broadening based ...

The effects of noise on recall of lists of associated words

Abstract: An experiment investigated the effect of noise on recall of lists consisting of pairs of strong and weak associates. Noise improved recall (both number recalled and organization of recall) and did so with both types of list. The subjects who were initially tested in noise continued to show better recall and organization of recall even when they were transferred to the quiet condition. This finding shows that noise may reinforce the use of the dominant strategy and that this strategy may be used more in noise when experimental conditions are changed and even when the subject is transferred from the noise to the quiet.

Interrupted noise as a tinnitus masker: an annoyance study

Abstract: Tinnitus can be masked by a simultaneous and/or nonsimultaneous stimuli. The usefulness of the masker depends on its power and its perceived annoyance. The purpose of the current study was to compare annoyance produced by interrupted and continuous noises. Data were gathered from six normal-hearing subjects without tinnitus and six subjects with tinnitus. Continuous white noise and interrupted white noise (2, 4, 10, 20, and 40 pulses per second) were presented at 20, 40, and 60 dB. Subjects adjusted the interrupted noise to be as annoying as the reference signal. The general findings were: (1) interrupted noises were more annoying than the continuous noises for both groups, and (2) the perception of annoyance in both groups was very similar at the highest level and significantly different at lower levels. For normal-hearing listeners, the differences between annoyance produced by continuous and interrupted noise were independent of the pulse rate for rates slower than 10 pulses per second, gradually decreasing for the higher rates. Despite the advantages of interrupted noise, it is not suitable as a tinnitus masker since it is more annoying than continuous noise.

Annoyance from audible infrasound

Abstract: For several years it has been known that noise at low and infrasonic frequencies can cause considerable nuisances. The annoyance cannot be predicted by A‐weighted sound levels since the A‐curve nearly removes the infrasonic frequencies completely and it also seems to attenuate the low audio frequencies too much. Recent work on equal loudness and equal annoyance contours indicates that the annoyance from infrasound is closely related to the loudness sensation. The use of a weighting curve based on the loudness and annoyance curves is suggested. The ISO/DIS 7196G1 curve might be a proper choice. The applicability of this curve is demonstrated. The experiments involve pure infrasonic tones as well as one‐third octave bands. The consequence of simultaneously occurring audio frequency noise is also demonstrated.

Automatic gain adjusting device of audio device

Abstract: PURPOSE:To prevent a reproduction sound from being masked owing to an noise and to improve a hearing sensation not only by varying a gain according to the level of the external noise and the level of an audio signal, but also by varying reproduction frequency characteristics. CONSTITUTION:A voltage DELTAVN corresponding to the increment DELTAN of the noise level is supplied from a noise detecting part 1 to a level converter 19, which outputs 0.3DELTAVN as its output voltage. Further, a voltage DELTAVS corresponding to the level increment DELTAS of the audio signal is supplied from a signal detecting part 9 to a level converter 20, which outputs 0.4DELTAVS as its output voltage. Therefore, the output voltage VG of a subtracter 21 is 0.3DELTAVN-0.4DELTAVS. The output voltage VG is digitized by an A/D converter 22 and supplied to a decoder driver 23, so light emitting diodes 24 which are proportional in number to the output voltage VG illuminate. A switch circuit 25 consists of plural transistors (TR) which turn on and off according to the output level of the decoder driver 23, and frequency characteristics of a variable characteristic circuit 26 vary according to on-off states of the TRs. The variable characteristic circuit 26 is interposed in an audio signal line and the constant in a variable gain circuit 2 is varied to vary the frequency characteristics.

An apparatus for reducing noise in audio signals

Abstract: In a rotary head magnetic recording and reproducing system of a helical-scan type for successively recording and reproducing audio signals in and from record patterns on a magnetic tape, which record patterns are inclined relative to the longitudinal direction of the magnetictape, by a magnetic head provided on a rotary cylinder, during the successive reproduction of the record patterns by the magnetic head, in order to prevent noise from being contained in a reproduced audio signal which noise is caused by the switching of the record patterns to be reproduced or by the occurrence of a dropout in the reproduced signal, an audio signal is divided into two discrete signals which have a phase difference therebetween and are transmitted respectively on two separate transmission paths. and two hold circuits (5, 7; 10,11), each of which is arranged in one of the two transmission paths, are put into operation in synchronism with the switching of the record patterns or the occurrence of the dropout in the reproduced signal, and output signals (G, H) of the two hold circuits (5, 7; 10, 11) are added together thereby to reduce noise contained in the reproduced output audio signal (H', L).

A method of processing audio information

Abstract: Stereo audio signals are processed by filtering low-frequency signals from each channel in a low- pass filter 10, amplifying the low-frequency signals at 12, and adding the resulting signal to the opposite channel. It has been found that this eliminates or reduces low-frequency noise caused by low- frequency vertical modulation, e.g. record warpage.

Video Recording with New Signal Processing

Abstract: Video recording systems such as VTRs generally use an emphasis method in signal processing to reduce noise generated in FM recording and reproduction, using a pre-emphasis circuit and a de-emphasis circuit. In recording, the high frequency components of the video signal are emphasized by the pre-emphasis circuit and, in reproduction, the emphasized components are suppressed by exactly the same amount by the de-emphasis circuit; this is very effective in reducing the FM noise, especially its high frequency components.

Emergency alarm broadcast receiver

Abstract: PURPOSE:To prevent the generation of a noise generated at the time of the start and the finish of an emergency alarm broadcast by generating a muting signal by using the output of a detecting part to detect the start signal or the finish signal of the emergency alarm broadcast, and stopping the operation of a sound amplifying part for a while. CONSTITUTION:When the emergency alarm broadcast is broadcast from a broadcasting station, the start signal is inputted to an alarm signal coincidence detecting part 10 through a normally operated tuner part 8, and the detecting part 10 detects it, and controls the reception indicator 12 of the emergency alarm broadcast and the sound amplifying part 9 into an operating state. Before it, a mute signal generating part 13 is driven by the output of the detecting part 10, and the noise to be generated at the time when the sound amplifying part 9 comes into the operating state is removed by stopping the operation of the sound amplifying part 9 for a short time by the muting signal. In the case of the termination of the emergency alarm broadcast as well, in a similar way to the start signal, the finish signal is detected, and by stopping the output of the sound amplifying part 9 for a short time by the muting signal generated from the mute signal generating part 13, the noise to be generated at the time when the sound amplifying part 9 comes into a non-operating state is removed.

White level detecting circuit of picture signal

Abstract: PURPOSE:To detect a correct white level without being affected by noise by providing a white level data storage means, comparing it with a white level data having an input picture signal data so as to allow the output to decrease or increase the white level. CONSTITUTION:A white level data of a picture signal is stored in an up-down counter 21. An input picture signal is given to a comparator 32 via a line 24 and compares with the white level data from the counter 21. When the level of the input picture signal is large, the white level of the counter 21 is increased. When the white level data from the counter 21 is larger, the white level data of the counter 21 is decreased. Thus, even when the white level is detected in error due to effect of noise or the like, the correct white level is detected.