Showing papers on "Noise published in 1974"

Reception of consonants in a classroom as affected by monaural and binaural listening, noise, reverberation, and hearing aids

Abstract: Reception of consonants was studied with normal‐hearing subjects in a sound‐treated classroom, at reverberation times T ≃0.3 and 0.6 sec, to compare binaural and monaural reception, with and without hearing aids, in the presence of an impulsive noise (16 imp/sec) and a quasisteady noise (a babble of eight voices). The consonants were spoken in words inbedded in a rapidly spoken carrier phrase. The speech and noise sources subtended an angle of 60° on a circle 11 ft in radius centered on the listener, to give a large advantage for binaural reception. Binaural gain was taken as the difference in speech‐to‐noise ratios for 60% correct reception comparing binaural and monaural results. The binaural gain at short reverberation, with unaided listening, was 5 dB in the presence of the babble and 4 dB in the presence of the impulsive noise. The introduction of hearing aids and the increase in reverberation each caused the binaural gain to decrease to 3 dB. The small increase in reverberation caused a substantial decrease in reception under the noise conditions tested. Analysis of the consonant responses to reflect reception of the phonetic features of voicing, manner, and place, for both initial and final consonants, indicated that the acoustic conditions of reverberation and binaural listening affected feature reception in predictable ways.

Threshold shift in the chinchilla from daily exposure to noise for six hours

Abstract: Trained chinchillas were exposed to 6 h of noise followed by 18 h of quiet for nine days. Thresholds (0.5–8.0 kHz) were measured immediately before and after each day’s exposure. The decay of threshold shift after the ninth day was followed until stable thresholds were again observed. This procedure was repeated for six levels (57–92 dB SPL) of an octave‐band noise centered at 4.0 kHz. The threshold shift measured after 4 min of quiet (TS4) appears to reach an asymptotic level (ATS4) after the first or second exposure. ATS4, measured at frequencies exhibiting greatest shift (5.7 kHz), increases with the level of the noise with the same slope (1.7 dB/dB) for the daily 6‐h exposures as for nearly continuous exposures. ATS4 is smaller for 6 h than nearly continuous exposures by about 5 dB and this difference can be explained by an equivalent‐power hypothesis. The decay of threshold shift was nearly complete after 18 h of quiet for the lowest levels of noise, while it was nearly complete only after 3–5 days for the intermediate levels of noise. The decay of threshold shift was never complete and small amounts of permanent threshold shift were observed for the highest levels of noise.

Noise in disk data-recording media

Abstract: Measurements were made of recording medium noise in erased disks using an in-contact magnetoresistive element and an inductive head supported on an air bearing slider. Four types of coatings on aluminum disks were examined: thin, transition-metal alloy film, CrO,, FeCo particle, a n d y-Fe,O:,. Results obtained by means of three measurement techniques are in qualitative agreement and indicate that: (1) dc-erased noi\\e of alloy film disks is 14 to 20 dB lower than that of particulate disks measured; (2) dc-erased noise of particulate disks measured is 6 to 16 dB above their bulk-erased noise: (3) although dc noise of particulate disks increases with write current, dc noise of alloy film disks is independent of write current: (4) the shapes of the noise spectra are similar in dc-erased particulate y-Fe,O, disks and FeCo particle coated disks: and (5) significant modulation noise is detected on particulate disks but not on alloy film disks. The observed dc-erased noise spectrum is compared with the model for small particle noise and is then used to estimate the size of particle agglomerates or voids. Introduction Several theoretical and experimental investigations of noise in magnetic tape systems have been published [ 1-61, but until recently there was little interest in measuring the corresponding noise in disk surface media because it does not limit performance of present disk data storage systems. Disk noise measurements are of theoretical interest because of the relatively well-known head-medium spacing and the expected absence of noise caused by surface irregularities, tape flutter, and inverse magnetostrictive effects associated with head-tape contact. Although most tape noise studies have emphasized the noise of ac-erased media, the emphasis here is on the dc-erased, or uniformly magnetized, state which resembles the saturated digital state. The dc-erase noise provides information about the homogeneity of the magnetic medium, and its measurement can shed light on the suit-ability of the medium for use at high storage densities. The difference between the observed noise power spectrum and that which would be caused by small particles is interpreted as the noise spectrum of the inhomogenei-ties. Measurements of particulate coatings, both here and in the literature, indicate higher noise levels for dc erase than for ac erase. For comparison, measurements are presented here of a thin transition-metal alloy film medium, for which the reverse is true.

The Effects of White Noise on the Frequency of Stuttering.

Abstract: Three adult male stutterers spoke spontaneously during a series of base-rate and noise sessions. Base rate was run first for a minimum of 100 minutes and until two criteria of stability were met. F...

Effect of Spread of Excitation on the Loudness Function at 250 Hz

Abstract: The loudness of a low-frequency 250-Hz tone was measured in quiet and in the presence of an adjacent band-pass noise. Loudness measurements were obtained by loudness matching, magnitude estimation, and magnitude production. Comparisons were made among the effects on loudness of the following noise bands: 390–2400 Hz, 345–2400 Hz, and 300–2400 Hz. The noise increased in intensity with the tone so that during a given listening session the signal-to-noise ratio remained constant at +10,0, or −l0dB. The data suggest that, when the high-frequency tail produced in the ear by the tone is completely masked, the effect of the noise is to decrease by 20% the slope (exponent) of the loudness function above 70 dB SPL. Otherwise, the loudness functions of the 250-Hz tone in noise and in quiet are essentially the same. The results are consistent with data available in the literature.

Most comfortable loudness for pure tones and speech in the presence of masking noise.

Abstract: Pure-tone and speech most-comfortable-loudness (MCL) levels were determined in noise and quiet. A Bekesy-type tracking task was used to determine the MCLs under all conditions. The subjects (N = 12...

Effect of cessation of late-night landing noise on sleep electrophysiology in the home

Abstract: Simultaneous measurements of noise exposure and sleep electrophysiology were made in homes before and after cessation of nighttime aircraft landing noise. Six people were tested, all of whom had been exposed to intense aircraft noise for at least two years. Noise measurements indicated a large reduction in the hourly noise level during nighttime hours, but no charge during the daytime hours. Sleep measures indicated no dramatic changes in sleep patterns either immediately after a marked change in nocturnal noise exposure or approximately a month thereafter. No strong relationship was observed between noise level and sleep disturbances over the range from 60 to 90 db(A).

Infrared sky noise survey

Abstract: A 10 micron infrared sky noise survey, which was conducted during the period from June 1, 1970 to June 30, 1974, is reported along with associated electronics and recording equipment which was developed and deployed for periods up to 18 months at various potential or existing infrared observing sites in the U.S., Mexico, and Chile. The results of the data activity are given, and variables are defined which influence the intensity and duration of the sky noise.

Audibility of infrasound

Abstract: The distortion of pure tones (1–16 Hz) caused by the nonlinearities of the middle ear was calculated. It is shown that the slope of the audibility curves for infrasound of Yeowart and Evans could be predicted, thus implying that infrasound might not be heard in the normal sense, but only heard as distortion after being transduced through the middle ear. To verify this result, subjects were exposed simultaneously with the 1–10‐Hz stimuli to a low‐frequency masking noise (10–100 Hz). This noise was shown to mask pure tones of infrasound of 1–10 Hz even when the SPLs of these tones were 15–25 dB above the masking noise overall sound‐pressure level. Clearly, this result implies that the pure tones of infrasound below 10 Hz are not heard in the same manner as tones above 16 Hz. The implications of these results to the importance of the infrasound components of any broad‐band noise and to the auditory effects of infrasound are discussed.

Data signaling noise suppression system

Abstract: The suppression of speaker noise caused by data signaling in a mobile radio system is achieved by detecting the presence of a single audio tone frequency over a time period and when the presence of such a tone is detected causing muting of the speaker of the mobile radio receiver.

Judged acceptability of noise exposure during television viewing

Abstract: Noise masking of television audio signals by flyovers is the most frequently mentioned problem of airport neighbors. This problem was studied in the laboratory using artificial noise. Three studies varied the intensity, duration, and rate (noises per hour) of the noises. Acceptability was found to approximate a logarithmic function of noise energy for changes in intensity, duration, and rate. Thus, the equal‐energy principle, which has been generally observed in abstract psychometric experiments, was confirmed in this more realistic and representative task. A fourth study showed aircraft‐flyover recordings to be more acceptable than artificial noises even though they had equivalent peak levels and masking durations. This difference can also be explained by the equal‐energy principle, since the flyovers had lower average (or integrated) energy.

Masking of filtered noise bursts by synthetic vowels

Abstract: The present investigation was designed to study temporal‐masking effects produced by speech‐like signals. The masking stimuli were computer‐generated vowel‐like signals; two durations (100 and 200 msec) of each of four vowel‐like signals were employed. The probe stimuli were three filtered noise bursts which differed in their spectral distribution. A noise burst preceded, followed, or occurred simultaneously with a vowel‐like signal. The maximum interstimulus interval was 100 msec. Masked thresholds were determined for four well‐trained subjects using the method of adjustment. The results were generally in accord with the findings of temporal‐masking studies in which nonspeech‐like stimuli were employed. The effects of the duration and spectral characteristics of the vowel‐like signals on detectability of the noise bursts are discussed. [Research supported by NINDS.]

Four-channel stereophonic reproducing system for reproducing discrete four-channel stereophonic discs

Abstract: In a four-channel stereophonic reproducing system of the type in which a first, second, third and fourth audio signals are reproduced from two stereophonic composite signals which are respectively comprised of a left side signal consisting of a main channel signal composed of the sum of the first and second audio signals and a sub-channel signal obtained by frequency modulating or phase modulating the difference between the first and second audio signals, and a right side signal consisting of a main channel signal composed of the sum of the third and fourth audio signals and a sub-channel signal obtained by frequency modulating or phase modulating the difference between the third and fourth audio signals, a detector circuit for detecting each sub-channel signal is followed by a filter circuit for eliminating undesired higher frequencies whereby to eliminate higher audio frequencies including increased noise components to improve the S/N ratio, and at the same time a phase correction circuit is provided in the reproducing section for each main channel signal to correct for any phase distortion due to the filter circuit whereby to ensure a greatly improved separation.

Shock Tolerance in Rats as a Function of White Noise

Abstract: Two groups of 10 rats each were trained to cross increasing levels of electrical shock in a straight alley runway for food. The group receiving masking white noise (88 db) showed a significantly higher shock tolerance than controls that received no white noise. The results were interpreted as supporting the audioanalgesic effect and as suggesting a need to examine the use of masking white noise in studies using shock

Psychological effects of exposure to high industrial noise: a field study

Abstract: A comparative investigation was carried out on two samples of industrial workers. One group (60 persons) working in noise (85–106 dB) and a control group (40 persons) working in relative quiet (under 82 dB). Noise annoyance and neuroticism were assessed by means of questionnaires, and performance level by two psychological tests, the Stroop test, and a test of concentration of attention. Comparisons between the two samples were performed as a function of age and of time worked in noise. It was found that neuroticism rises primarily as a function of time worked in noise and secondarily as a function of age. There is a critical age or time interval after which neuroticism develops quickly. It was also found that, as compared to the control group, the noise group (1) manifests greater annoyance, but only after two years on the job; (2) displays a higher ability to focus attention; but (3) makes more errors on the Stroop psychological performance test and fers a higher degree of interference with performance.

Spectral analyses in truck tire noise fields

Abstract: This paper discusses the importance of the spectral distribution of the energy in the sound to the dB(A) level of the usual passby test. A described technique obtains reproducible "real-time" spectra from the nonstationary sound field. Doppler effect and source frequency shift are quantified in relating these spectra to the tread pattern repetitions. Inverse square law fitting is viewed through the two-source-microphone relation which changes during the spectral window period. Spectra are shown for 6, 12, and 50 ft (1.83, 3.66, and 15.2 m) passby microphones and for a microphone carried on the truck.