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At least 397 records · Page 22Linked to original sources
PubMed1980

Auditory intensity discrimination in blackbirds and pigeons.

Redwing blackbirds, brown-headed cowbirds, and pigeons were trained with operant conditioning techniques to respond to small increases in the intensity of pulsed tone trains at three frequencies: .5, 1.0, and 2.0 kHz. All three species produced similar intensity difference limens (DLs) at the frequencies tested. Intensity DLs decreased as sensation level (intensity level above absolute threshold) increased at all three frequencies, with the slopes of these sensation level functions being greatest at 2.0 kHz . The median intensity DLs at 50 dB sensation level were 3.3, 2.7, and 2.9 dB at .5, 1.0, and 2.0 kHz, respectively, averaged over the three species. Some subjects were also required to detect decreases in intensity. They produced intensity DLs two to three times larger than the DLs obtained when these same subjects were required to detect increases in intensity. Avian intensity DLs generally appear to be 1-2 dB higher than the DLs of those mammals that have been tested (rat, cat, monkey, humans).

Animals↗
PubMed2005

Neural population coding of sound level adapts to stimulus statistics.

Mammals can hear sounds extending over a vast range of sound levels with remarkable accuracy. How auditory neurons code sound level over such a range is unclear; firing rates of individual neurons increase with sound level over only a very limited portion of the full range of hearing. We show that neurons in the auditory midbrain of the guinea pig adjust their responses to the mean, variance and more complex statistics of sound level distributions. We demonstrate that these adjustments improve the accuracy of the neural population code close to the region of most commonly occurring sound levels. This extends the range of sound levels that can be accurately encoded, fine-tuning hearing to the local acoustic environment.

Acoustic Stimulation↗
PubMed1992

[Various uncomfortable loudness thresholds, their correlation and use in general practice].

In the present study we examined the relationship of the loudness discomfort level LDL of different signals. We carried out measurements in 97 patients, all of whom suffered from a sensorineural hearing loss. The results showed almost no difference between the LDL of pure tones and narrow band noise. The LDL of broad band noise showed a good correlation to the LDL of 250 Hz. Only the LDL of monosyllables ranged at a higher SPL. For an up-to-date hearing aid fitting, all forms of LDL should be taken into consideration. This is especially necessary when using digital hearing aids.

Adolescent↗
PubMed2006

A longitudinal study of electrical stimulation levels and electrode impedance in children using the Clarion cochlear implant.

CONCLUSIONS: Electrical stimulation levels and electrode impedance values (EIVs) in children using the Clarion cochlear implant (CI) programmed with CIS strategy stabilized after 3 months of implant use. The data presented here may be useful as a general guideline for the programming of infants and young children and may further be of help for the identification of patients who fall outside the "average" range. OBJECTIVES: The purpose of the present study was to evaluate changes in electrical stimulation levels, i.e. threshold (T) levels, comfortable (M) levels, dynamic range (DR), and EIVs during the first 18 months of implant use, in children using the Clarion CI. MATERIALS AND METHODS: The maps of 18 pre-lingual children (mean age at implantation 4.2 years; range 1-8), using the Enhanced Bipolar 1.2 or Bipolar standard electrode with the S-Series speech processor programmed with CIS strategy, were examined at five time points: connection, and 3, 6, 12, and 18 months post-initial stimulation. T levels, M levels, DR and EIVs were analyzed according to four cochlear segments: apical, apical-medial, medial-basal, and basal. RESULTS: During the first 3 months of implant use T levels increased to some extent, whereas M levels and DR increased significantly. From 3 months and through the entire follow-up, T and M levels as well as DR were stable. EIVs of current carrying electrodes decreased significantly from connection to the 3-month visit; thereafter a stabilization of values was evident. Electrical stimulation levels and EIVs did not differ among the cochlear segments during the entire follow-up.

Adolescent↗
PubMed1992

Tonotopic organization of human auditory cortex revealed by multi-channel SQUID system.

A 14-channel SQUID (superconducting quantum interference device) system has been used to record the magnetic signal from the human brain in response to an auditory stimuli (750, 1,000, 1,250 and 1,500 Hz, 70, 76 and 82 dB SPL, 500 ms duration). Three individuals with normal hearing were studied. The locations of magnetic response at the latency of 70 ms (P70), 100 ms (N100) and 160 ms (P160) from the onset of the auditory stimulus were identified. The location for N100 response corresponded to the primary auditory cortex (area 41), where a clear tonotopic organization was demonstrated. The amplitopic organization was less evident. These results suggest a flow of auditory signals in the temporal lobe and tonotopic organization in the auditory cortex.

Auditory Cortex↗
PubMed1996

The illusion of increasing loudness in brief steady tones: variation with carrier frequency.

A brief tone of steady intensity is heard as growing louder; to be heard as steady, intensity must be decreasing. The present report concerns the influence of carrier frequency on this illusion. Stimuli each lasted 1.5 s, during which time intensity was increasing, decreasing, or remaining steady; the initial intensity was 40 dB SPL (sound pressure level relative to 0.0002 dynes/cm2). Carrier frequencies were between 0.0625 and 8.0 kHz. Four listeners made forced binary responses of "growing louder" or "growing softer" to stimuli. Values of changing intensity that elicited equal numbers of each type of response were computed. As expected, these values were negative. The illusion was most pronounced for the lowest and highest frequencies. In contrast to the results of a recent study, the findings were that sensitivity to changing intensity did not vary systematically with the size of the illusion. The illusion might arise because many sounds slowly decay in intensity and because of the importance of detecting approaching sound sources, analogous to "looming" in the visual modality. Overall loudness of the sound source should assist in altering the listener; the increase in the illusion at the extremities of the frequency range might compensate for the reduced overall loudness at such frequencies.

Adult↗
PubMedDate not supplied

Stimulus, response, and state variables in the testing of neonates.

This paper endeavors to answer three closely related questions: What motor behavior displayed by an infant may be considered to be a response to acoustic stimulation? What acoustic phenomena elicit such behavior? Does responsiveness vary with postconceptual age? Review of our work over the past decade reveals that we know the answers to the first two questions, but not the third. Briefly, arousal responses (eye and limb movements) are reliably elicited by wideband signals but not by narrowband signals. However, there is still confusion about whether preterm infants are more or less responsive than full term infants.

Acoustic Stimulation↗
PubMed2001

Melody lead in piano performance: expressive device or artifact?

As reported in the recent literature on piano performance, an emphasized voice (the melody) tends to be played not only louder than the other voices, but also about 30 ms earlier (melody lead). It remains unclear whether pianists deliberately apply melody lead to separate different voices, or whether it occurs because the melody is played louder (velocity artifact). The velocity artifact explanation implies that pianists initially strike the keys simultaneously; it is only different velocities that make the hammers arrive at different points in time. The measured note onsets in these studies, mostly derived from computer-monitored pianos, represent the hammer-string impact times. In the present study, the finger-key contact times are calculated and analyzed as well. If the velocity artifact hypothesis is correct, the melody lead phenomenon should disappear at the finger-key level. Chopin's Ballade op. 38 (45 measures) and Etude op. 10/3 (21 measures) were performed on a Bösendorfer computer-monitored grand piano by 22 skilled pianists. The hammer-string asynchronies among voices closely resemble the results reported in the literature. However, the melody lead decreases almost to zero at the finger-key level, which supports the velocity artifact hypothesis. In addition to this, expected onset asynchronies are predicted from differences in hammer velocity, if finger-key asynchronies are assumed to be zero. They correlate highly with the observed melody lead.

Artifacts↗
PubMed2001

Basilar-membrane response to multicomponent stimuli in chinchilla.

The response of chinchilla basilar membrane in the basal region of the cochlea to multicomponent (1, 3, 5, 6, or 7) stimuli was studied using a laser interferometer. Three-component stimuli were amplitude-modulated signals with modulation depths that varied from 25% to 200% and the modulation frequency varied from 100 to 2000 Hz while the carrier frequency was set to the characteristic frequency of the region under study (approximately 6.3 to 9 kHz). Results indicate that, for certain modulation frequencies and depths, there is enhancement of the response. Responses to five equal-amplitude sine wave stimuli indicated the occurrence of nonlinear phenomena such as spectral edge enhancement, present when the frequency spacing was less than 200 Hz, and mutual suppression. For five-component stimuli, the first, third, or fifth component was placed at the characteristic frequency and the component frequency separation was varied over a 2-kHz range. Responses to seven component stimuli were similar to those of five-component stimuli. Six-component stimuli were generated by leaving out the center component of the seven-component stimuli. In the latter case, the center component was restored in the basilar-membrane response as a result of distortion-product generation in the nonlinear cochlea.

Animals↗
PubMed2002

Intensity-importance functions for bandlimited monosyllabic words.

A study was carried out to determine the relative importance to speech intelligibility of different intensities within the speech dynamic range. The functions that were derived are analogous to previous descriptions of the relative importance of different frequencies and are referred to here as intensity-importance functions (IIFs). They were obtained as follows. Sharply filtered bands of speech (NU6 monosyllabic words) were mixed with filtered noise and presented alone or in pairs at 19 signal-to-noise ratios (-25 to 41 dB). When paired bands were tested, the level and signal-to-noise ratio (SNR) of one band were held constant while the level and SNR of the other band were varied. The listeners were 100 normal hearers, organized into five 20-person groups. Each group provided speech recognition data for one of five frequency regions (141-562, 562-1122, 1122-1778, 1778-2818, and 2818-8913 Hz). Comparisons of the results for each group indicated that IIFs vary with frequency and SNR. Current methods for predicting intelligibility from physical measurements of speech audibility would need to be revised in order to take such findings into consideration.

Adult↗
PubMed2002

Spectral loudness summation as a function of duration.

Loudness was measured as a function of signal bandwidth for 10-, 100-, and 1000-ms-long signals. The test and reference signals were bandpass-filtered noise spectrally centered at 2 kHz. The bandwidth of the test signal was varied from 200 to 6400 Hz. The reference signal had a bandwidth of 3200 Hz. The reference levels were 45, 55, and 65 dB SPL. The level to produce equal loudness was measured with an adaptive, two-interval, two-alternative forced-choice procedure. A loudness matching procedure was used, where the tracks for all signal pairs to be compared were interleaved. Mean results for nine normal-hearing subjects showed that the magnitude of spectral loudness summation depends on signal duration. For all reference levels, a 6- to 8-dB larger level difference between equally loud signals with the smallest (delta f = 200 Hz) and largest (delta f = 6400 Hz) bandwidth is found for 10-ms-long signals than for the 1000-ms-long signals. The duration effect slightly decreases with increasing reference loudness. As a consequence, loudness models should include a duration-dependent compression stage. Alternatively, if a fixed loudness ratio between signals of different duration is assumed, this loudness ratio should depend on the signal spectrum.

Adult↗
PubMed2003

Factors contributing to bone conduction: the outer ear.

The ear canal sound pressure and the malleus umbo velocity with bone conduction (BC) stimulation were measured in nine ears from five cadaver heads in the frequency range 0.1 to 10 kHz. The measurements were conducted with both open and occluded ear canals, before and after resection of the lower jaw, in a canal with the cartilage and soft tissues removed, and with the tympanic membrane (TM) removed. The sound pressure was about 10 dB greater in an intact ear canal than when the cartilage part of the canal had been removed. The occlusion effect was close to 20 dB for the low frequencies in an intact ear canal; this effect diminished with sectioning of the canal. At higher frequencies, the resonance properties of the ear canal determined the effect of occluding the ear canal. Sectioning of the lower jaw did not significantly alter the sound pressure in the ear canal. The sound radiated from the TM into the ear canal was investigated in four temporal bone specimens; this sound is significantly lower than the sound pressure in an intact ear canal with BC stimulation. The malleus umbo velocity with air conduction stimulation was investigated in nine temporal bone specimens and compared with the umbo velocity obtained with BC stimulation in the cadaver heads. The results show that for a normal open ear canal, the sound pressure in the ear canal with BC stimulation is not significant for BC hearing. At threshold levels and for frequencies below 2 kHz, the sound in the ear canal caused by BC stimulation is about 10 dB lower than air conduction hearing thresholds; this difference increases at higher frequencies. However, with the ear canal occluded, BC hearing is dominated by the sound pressure in the outer ear canal for frequencies between 0.4 and 1.2 kHz.

Auditory Threshold↗
PubMed2006

Induced loudness reduction as a function of exposure time and signal frequency.

Induced loudness reduction (ILR) is the decline in the loudness of a weaker tone induced by a preceding stronger tone. In this study we investigate how ILR depends on exposure time and signal frequency. For 12 listeners, successive magnitude estimation was used to measure the loudness of 70-dB-SPL test tones, presented with and without preceding 80-dB-SPL inducer tones at the same frequency. Experiment 1 measured the evolution of ILR over time at 0.5 kHz. The results suggest that ILR may begin after a single inducer presentation, and increases over at least 2 to 3 min as the inducer and test tones are repeated every few seconds. Following the cessation of the inducer, the recovery of loudness is slow and still incomplete after 1 min. Experiment 2 extended the measurements to additional signal frequencies. The results show that the amount of ILR and its evolution over time are approximately the same at frequencies from 0.5 to 8 kHz. Similarly, loudness matching showed no effect of frequency on ILR, which averaged 8.2 dB. These findings, together with previously noted similarities among ILR, ipsilaterally induced loudness adaptation, and temporary loudness shift, indicate that loudness reduction induced by stronger sounds is a very common phenomenon.

Acoustic Stimulation↗
PubMed1984

The influence of pinnae-based spectral cues on sound localization.

The role of pinnae-based spectral cues was investigated by requiring listeners to locate sound, binaurally, in the horizontal plane with and without partial occlusion of their external ears. The main finding was that the high frequencies were necessary for optimal performance. When the stimulus contained the higher audio frequencies, e.g., broadband and 4.0-kHz high-pass noise, localization accuracy was significantly superior to that recorded for stimuli consisting only of the lower frequencies (4.0- and 1.0-kHz low-pass noise). This finding was attributed to the influence of the spectral cues furnished by the pinnae, for when the stimulus composition included high frequencies, pinnae occlusion resulted in a marked decline in localization accuracy. Numerous front-rear reversals occurred. Moreover, the ability to distinguish among sounds originating within the same quadrant also suffered. Performance proficiency for the low-pass stimuli was not further degraded under conditions of pinnae occlusion. In locating the 4.0-kHz high-pass noise when both, neither, or only one ear was occluded, the data demonstrated unequivocally that the pinna-based cues of the "near" ear contributed powerfully toward localization accuracy.

Auditory Perception↗