摘要:

Response patterns (PST histograms) of auditory nerve fiber discharges with two‐tone stimuli were obtained. The two tones either overlapped (simultaneous suppression) or were temporally separated (forward suppression). The response elicited by a probe tone at the fiber's CF decreases when immediately preceded by a masking tone. It was found that the frequency/intensity combinations of effective maskers lie within the tuning curve of the fiber. In simultaneous two‐tone suppression the frequency/intensity contours of the masker are broader than those observed in the forward suppression condition. The post stimulus suppression in firing below spontaneous rate, which is typically observed following maintained excitation, is suggested as the single‐fiber substrate for forward suppression and masking effects observed in AP and psychophysics. [Supported by Grants from the NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2003549

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Decreases in sound attenuation resulting from acoustic arousal of the middle‐ear‐muscle reflex were investigated during an 8‐h exposure to an octave band of noise centered at 0.5 kHz at 95 dB SPL. Chinchillas were chronically implanted with round‐window recording electrodes. Changes in the amplitude of the cochlear microphonic during continuous noise exposure reflected activity of the acoustic reflex (AR). The 8‐h exposure was composed of four consecutive 2‐h periods separated by 11‐min “quiet” intervals. The AR remained active throughout each of the four exposures, but the magnitude of the reflex decreased approximately 30%–50% within each 2‐h period. This decaying process appeared to reach an equilibrium following 8–30 min of exposure after which a constant level of effect was maintained. The initial magnitude of attenuation measured after noise onset decreased with each additional exposure period.

ISSN:0001-4966    

DOI:10.1121/1.2003555

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Results are provided which contribute to establishment of noise levels that are compatible with residential living activities. Community‐noise simulation systems were placed in the homes of 24 families that werenotimpacted by airport noise. Each family was exposed to four different airport noise conditions of one week duration. Interference with daily living activities and annoynace responses to the four conditions were obtained. Some results and conclusions are as follows: (1) Noise from other sources within their homes bothered or annoyed the participants as much or more than the flyover noises. (2) Behavioral awakening did not occur for many participants exposed to night flyovers peaking at approximately 70 dBA. It was concluded that the 10 dB penalty applied to night flyovers for NEF andLdnis too large. (3) For the mix and number of aircraft utilized, it was concluded that a NEF of 32 to 33 is compatible with indoor residential living. [FAA‐RD supported.]

ISSN:0001-4966    

DOI:10.1121/1.2003559

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Airport noise is easily the most intensive, publicized, and emotional noise problem facing urban dwellers. The problem is also a magnificent example of federal inaction, and technical doubletalk as a result of its complexity. The Minneapolis—St. Paul International Airport, even though singular in innovative noise abatement procedures developed under public pressures, continued to unacceptably impact the life and property of its neighbors. In facing the problem, the Agency encountered: lack of successful case histories, unmeasurable criteria, unaffordable instrumentation, and noncooperation by federal agencies and industry. Roadblocks were overcome steadily: Noise Standards were adopted in November 1974; automatic noise monitors were developed at reasonable prices ($200 per unit) and 33 units purchased; a monitoring program with the help of 350 families was implemented, the impact of the problem was defined acoustically and demographically, unique operational characteristics of airline companies uncovered and documented and an objective dialogue with the source started. State Regulations on this problem are being developed to control areas where voluntary compliance is not expected and to supplement recent legislative action.

ISSN:0001-4966    

DOI:10.1121/1.2003564

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The current status of standards under preparation will be discussed. In addition to those topics of interest including hearing conservation, noise dosimeters, hearing aids, etc., consideration will be given to new standards which might be needed over the next few years. A report from the S3 Subcommittee on Noise will be presented.

ISSN:0001-4966    

DOI:10.1121/1.2003571

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Five monaural chinchillas were exposed to a repetitive, reverberant, impulse noise for ten days. The impulse‐noise source was a mechanized hammer pounding on a steel plate at a rate of 1 impulse/sec. The average, peak over‐pressure within the holding cage was 113 dB SPL. Auditory thresholds were determined before and after exposure at 0.5, 1, 1.4, 2. 2.8, 4, 8, and 16 kHz by means of a behavioral technique utilizing shock‐avoidance conditioning. During exposure, thresholds at 0.5 and 8 kHz were monitored on a daily basis. Within eight hours from the start of the exposure, threshold shifts at both frequencies had reached asymptotic levels of from 30 to 40 dB. Upon removal from the noise, the threshold shift at 8 kHz recovered more rapidly than at 0.5 kHz; however, at 40 days, both had returned to within 10 dB of the pre‐exposure thresholds. A maximum PTS of 20–30 dB was found at either 2 or 2.8 kHz. Cochleagrams were obtained for each animal 60 days following the exposure. The histological examination provided support for the audiological findings.

ISSN:0001-4966    

DOI:10.1121/1.2003575

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Mongolian gerbils were trained in a shuttlebox avoidance task and their auditory thresholds determined. Groups of six subjects each were exposed to a two‐octave (1414–5656 Hz) band of noise for one hour at intensities of 100, 110, and 120 dB SPL. Thresholds between 0.1 and 16.0 kHz were determined 0.5, 3.0, 6.0, and 12.0 hours after exposure, and daily for 27 days. Final threshold determinations were made at least two months postexposure. A temporary threshold shift (TTS) was observed in all groups, the extent of which increased with increasing intensity of exposure. Recovery of thresholds followed an exponential course, and for extensive TTS lasted throughout the 28‐day observation period. In some cases additional recovery was noted upon final threshold determination. No significant permanent threshold shift (PTS) was seen in the 100‐dB exposure group, but PTS did occur in the 110‐and 120‐dB groups. PTS was limited to a relatively narrow band of frequencies, and exhibited a half‐octave shift toward higher frequencies. In terms of both TTS and PTS, the gerbil appears to be less sensitive to noise than chinchillas exposed to the same stimulus. [Work supported by NINCDS and the Medical Research Service of the Verterans Administration.]

ISSN:0001-4966    

DOI:10.1121/1.2003577

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The apparatus and training necessary to test cats in a two‐response‐key auditory discrimination and choice reaction time paradigm is described. Cats initiated a cycle of the discrete trial procedure by depressing two response pedals and holding them down until a light which marked the trials occurred. During trials, release of the right and left response pedals were defined as reports of tone presence and tone absence respectively. Correct release responses were reenforced with liquid food. Incorrect responses or failures to respond were not reenforced. Trials were terminated by a response or after 1.6 sec, whichever came first. Reaction times were defined as the time from trial onset until the occurrence of a response. Operation of the system was demonstrated with the method of constant stimuli. Half the trials were blanks in which no tone was presented; on the remaining trials each of 4 SPL of an 8‐kHz tone were equally likely. Detection was direct function of tone intensity and median reaction time to correctly report the presence of the tone was an inverse function of tone intensity. [Supported by Research Grant NSO5077 and Program Project Grant NSO5785 from NINCDS.]

ISSN:0001-4966    

DOI:10.1121/1.2003584

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

The ability of monkeys (Macaca) to detect a change in the location of a sound in space was psychophysically assessed through the employment of operant‐conditioning techniques. Contact with a response disk initiated a train of acoustic stimuli pulsed from a standard location (0° azimuth). Following a variable number of pulses the stimulus changed its spatial position to one of several comparison locations. If the monkey reported this change in location by releasing the response disk it received food for reenforcement. Thresholds for the minimum discriminable change in the horizontal coordinate of sound in space (azimuth) were determined by the method of constant stimuli under free‐field conditions in an anechoic chamber. The monkeys were tested with a parametric array of pure tones and signals of different bandwidths. The results indicate that the inverse relationship between threshold and stimulus bandwidth found in a preliminary study [C. H. Brown, M. D. Beecher, D. B. Moody, and W. C. Stebbins, J. Acoust, Soc. Am.58, 124S (1975)] characterizesMacacalocalization over much of its range of hearing. [This research was supported by NSF Grant No. BMS74‐20050 and Program Project Grant NSO5785.]

ISSN:0001-4966    

DOI:10.1121/1.2003590

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP

摘要:

Aural tests were done for stimuli consisting of three‐vowel chain synthesized by means of terminal‐analog speech synthesizer. The second‐formant frequency corresponding to the middle vowel of the stimuli changed along a stimulus continuum from /u/ to /i/, while other formants were held constant. The initial and final vowels of the stimuli were the same vowel /u/, and the duration and frequency of the second formant corresponding to the middle vowel had different values. The formant transition changed linearly with different rates. Subjects identified the middle vowel of each stimulus as one of Japanese vowels /u/ or /i/. The results indicated that the changed rate of the formant transition and the duration of the midpart of steady state had little effect on vowel perception if the whole duration between the initial and final vowels became longer than 50 msec.

ISSN:0001-4966    

DOI:10.1121/1.2003599

出版商:Acoustical Society of America    

年代:1976

数据来源: AIP