Loudness Of Pure Tones Research Articles

Effect of the Interaural Time Difference on the Loudness of Pure Tones as a Function of the Frequency

Significant loudness variations with source azimuth (i.e. directional loudness) are generally accounted for by at-ear pressure modifications. An effect of the interaural time difference (ITD) was also reported in previous studies by the authors: the loudness of pure tones (200 and 400 Hz) significantly increased when the stimuli were presented with an ITD of 772 μs, corresponding to an azimuth of 90°. The present study aims at observing this effect for higher frequencies, including frequencies at which ITD is no longer useful as a localization cue. The effect of ITD on the loudness of pure tones was thus studied at 500, 707, 1000, 1404 and 2000 Hz. Results show that the effect of ITD on loudness is not significant above 500 Hz, even for frequencies where ITD is still a localization cue. The effect observed at 500 Hz is still in agreement with the results reported by previous studies as the loudness of a pure tone significantly increases when its ITD is 772 μs.

Effects of masker envelope coherence on intensity discrimination

Masked detection threshold for a pure tone signal depends on the coherence of masker envelope fluctuation across frequency, with lower thresholds for coherent fluctuation under some conditions. The benefit of coherent masker modulation is larger for detection than for suprathreshold tasks, such as pure tone intensity discrimination [Hall, J. W. and Grose, J. H. (1995). J. Acoust. Soc. Am. 98, 847-852]. In the present study, sensitivity to increments in signal intensity was measured for a 1000-Hz signal, either a tone or a 20-Hz-wide narrowband noise. In one set of conditions the masker was one or more bands of noise, each 20 Hz wide, and in another set of conditions the masker was a single 1620-Hz-wide band of Gaussian noise or noise multiplied by the envelope of a 20-Hz bandpass noise. Coherent masker envelope fluctuation improved detection thresholds in all conditions. Intensity discrimination for a tonal standard in comodulated noise was elevated for standard levels near detection threshold and improved with increasing signal-to-noise ratio, whereas performance was uniformly poor across level for the noise standard. Results are most consistent with the interpretation that the reduced benefit of coherent masker modulation in suprathreshold intensity discrimination is due to the disruptive effects of envelope fluctuation.

Psychometric functions for pure tone intensity discrimination: Slope differences in school-aged children and adults

Previous work on pure tone intensity discrimination in school-aged children concluded that children might have higher levels of internal noise than adults for this task [J. Acoust. Soc. Am. 120, 2777-2788 (2006)]. If true, this would imply that psychometric function slopes are shallower for children than adults, a prediction that was tested in the present experiment. Normal hearing children (5-9 yr) and adults were tested in a two-stage protocol. The first stage used a tracking procedure to estimate 71% correct for intensity discrimination with a gated 500 Hz pure tone and a 65 dB sound pressure level standard level. The mean and standard deviation of these tracks were used to identify a set of five signal levels for each observer. In the second stage of the experiment percent correct was estimated at these five levels. Psychometric functions fitted to these data were significantly shallower for children than adults, as predicted by the internal noise hypothesis. Data from both stages of testing are consistent with a model wherein performance is based on a stable psychometric function, with sensitivity limited by psychometric function slope. Across observers the relationship between slope and threshold conformed closely to predictions of a simple signal detection model.

Psychometric functions for pure tone intensity discrimination: Slope differences in school-aged children and adults

Psychometric functions for pure tone intensity discrimination: Slope differences in school-aged children and adults

Across-channel interference in intensity discrimination: the role of practice and listening strategy.

Pure tone intensity discrimination thresholds can be elevated by the introduction of remote maskers with roved level. This effect is on the order of 10 dB [10 log(DeltaII)] in some conditions and can be demonstrated under conditions of little or no energetic masking. The current study examined the effect of practice and observer strategy on this phenomenon. Experiment 1 included observers who had no formal experience with intensity discrimination and provided training over 6 h on a single masked intensity discrimination task to assess learning effects. Thresholds fell with practice for most observers, with significant improvements in six out of eight cases. Despite these improvements significant masking remained in all cases. The second experiment assessed trial-by-trial effects of roved masker level. Conditional probability of a "signal-present" response as a function of the rove value assigned to each of the two masker tones indicates fundamental differences among observers' processing strategies, even after 6 h of practice. The variability in error patterns across practiced listeners suggests that observers approach the task differently, though this variability does not appear to be related to sensitivity.

Identification variability as a measure of loudness: An application to gender differences.

It is well known that discrimination response variability increases with stimulus intensity, closely related to Weber's Law. It is also an axiom that sensation magnitude increases with stimulus intensity. Following earlier researchers such as Thurstone, Garner, and Durlach and Braida, we explored a new method of exploiting these relationships to estimate the power function exponent relating sound pressure level to loudness, using the accuracy with which listeners could identify the intensity of pure tones. The log standard deviation of the normally distributed identification errors increases linearly with stimulus range in decibels, and the slope, a, of the regression is proportional to the loudness exponent, n. Interestingly, in a demonstration experiment, the loudness exponent estimated in this way is greater for females than for males.

Loudness for tone underwater

The loudness for pure tones was measured by loudness matching for 1-s pure tones from 100 to 50<th>000 Hz. The standard tone was 1000 Hz. Subjects were instructed to match the loudness of the comparison tone at one of the test frequencies to the loudness of the standard tone. The standard was presented at one of five sound pressure levels (SPL) for each set of frequencies. The standard SPL was varied randomly across test series. The subjects were bareheaded US Navy divers tested at a depth of 3 m. All subjects had normal hearing. The tones were presented to the right side of the subject from an array of underwater sound projectors. The SPL was calibrated at the location of the subject’s head with the subject absent. The loudness increased more rapidly as a function of standard SPL at mid-frequencies than at either high or low frequencies. The most compact loudness contours (least SPL change across range of standard SPL) were at 50<th>000 Hz. The underwater loudness contours across frequency are significantly different from in-air measurements and have a minimum in the 1000 Hz region rather than the 2–4 kHz region observed for in-air measurements. [Work supported by ONR.]

Underwater loudness for tones

The loudness for pure tones was measured by loudness matching for 1-s pure tones from 100 to 50<th>000 Hz. The standard tone was 1000 Hz. Subjects were instructed to match the loudness of the comparison tone at one of the test frequencies to the loudness of the standard tone. The standard was presented at one of five sound pressure levels (SPL) for each set of frequencies. The SPL was varied randomly across a test series. The subjects were bareheaded U.S. Navy divers tested at a depth of 3 m. All subjects had normal hearing. The tones were presented to the right side of the subject from an array of underwater sound projectors. The SPL was calibrated at the location of the subject’s head with the subject absent. The loudness increased more rapidly as a function of standard SPL at mid-frequencies than at either high or low frequencies. The most compact loudness contours (the least SPL change across the range of standard SPL) were at the highest frequency. Loudness contours across frequency derived from these measurements are significantly different from in-air measurements with minimum audibility in the 1000 Hz region rather than the 2–4 kHz region observed for in-air measurements.

Sources of variation in profile analysis. I. Individual differences and extended training.

This study investigated two sources of variance in the ability to discriminate auditory profiles: individual differences and extended training. The goals of the study were (1) to determine the range and origins of individual differences in profile analysis and (2) to determine whether those who initially had poor sensitivity to changes in spectral shape could eventually acquire finer sensitivity. Profile stimuli had 11 components with equal-log spacing from 200-2200 Hz. Thresholds ranged from - 1 to -25 dB (signal level relative to the context level) across 46 listeners. The correlation between spectral-shape discrimination thresholds after 2000 trials and pure-tone intensity-discrimination thresholds was 0.36. The range of individual differences for pure-tone intensity discrimination and spectral-shape discrimination was about the same. Two groups of listeners were given extended practice on the profile task, one group that showed low thresholds after an initial 2000 trials of practice and another that showed much higher initial thresholds. All listeners improved during the course of the first 2000 trials of training. Most of the poor listeners continued to improve during 9000 trials of training. Individual differences in the listeners' sensitivity to changes in spectral shape still existed after the extended practice.

Modeling the relation between the intensity just-noticeable difference and loudness for pure tones and wideband noise

A classical problem in auditory theory is the relation between the loudness L(I) and the intensity just-noticeable difference (JND) ΔI(I). The intensity JND is frequently expressed in terms of the Weber fraction defined by J(I)≡ΔI/I because it is anticipated that this ratio should be a constant (i.e., Weber’s law). Unfortunately, J(I) is not a constant for the most elementary case of the pure tone JND. Furthermore it remains unexplained why Weber’s law holds for wide-band stimuli. We explore this problem and related issues. The loudness and the intensity JND are defined in terms of the first and second moments of a proposed random decision variable called the single-trial loudness L̃(I), namely the loudness is L(I)≡EL̃(I), while the variance of the single trial loudness is σL2≡E(L̃−L)2. The JND is given by the signal detection assumption ΔL=d′σL, where we define the loudness JND ΔL(I) as the change in loudness corresponding to ΔI(I). Inspired by Hellman and Hellman’s recent theory [J. Acoust. Soc. Am. 87, 1255–1271 (1990)], we compare the Riesz [Phys. Rev. 31, 867–875 (1928)] ΔI(I) data to the Fletcher and Munson [J. Acoust. Soc. Am. 5, 82–108 (1933)] loudness growth data. We then make the same comparison for Miller’s [J. Acoust. Soc. Am. 19, 609–619 (1947)] wideband noise JND and loudness match data. Based on this comparison, we show empirically that ΔL(L)∝L1/p, where p=2 below ≈5 sones and is 1 above. Since ΔL(I) is proportional to σL, when p=2 the statistics of the single-trial loudness L̃ are Poisson-like, namely σL2∝L. This is consistent with the idea that the pure tone loudness code is based a neural discharge rate (not the auditory nerve). Furthermore, when p=1 (above about 5 sones), the internal loudness signal-to-noise ratio is constant. It is concluded that Ekman’s law (ΔL/L is constant) is true, rather than Weber’s law, in this loudness range. One of the main contributions of this paper is its attempt to integrate Fletcher’s neural excitation pattern model of loudness and signal detection theory.

Neural contributions to the perstimulus compound action potential: implications for measuring the growth of the auditory nerve spike count as a function of stimulus intensity.

The perstimulus compound action potential (PCAP), unlike the more familiar compound action potential (CAP), can be recorded in response to asynchronous as well as synchronous auditory nerve activity. When all neurons contribute equally to the PCAP, the area under the PCAP (the PCAP area) is proportional to the number of action potentials fired by auditory nerve neurons (the auditory nerve spike count). The auditory nerve spike count is one proposed code for stimulus intensity, and our goal is to use the PCAP to test this hypothesis. In this study, two independent tests were developed to measure the contributions of neurons to the PCAP as a function of their characteristic frequency (CF). The test results were verified using a model of the auditory periphery designed to calculate the auditory nerve spike count as a function of pure tone intensity and frequency. In nearly all experiments, neurons having CFs that span contiguous three or four octave bands contribute equally to the PCAP. For pure tones that stimulate only those neurons contributing equally to the PCAP, the PCAP area grows over intensity ranges frequently exceeding 80 dB, and in one case equaling 108 dB. These results demonstrate that the auditory nerve spike count, at least for pure tones, is capable of encoding changes in stimulus intensity over the entire dynamic range of the auditory system.

Overshoot and the ‘‘severe departure’’ from Weber’s law

The link between the two phenomena of overshoot and the ‘‘severe departure’’ from Weber’s law in intensity discrimination was investigated. Masked thresholds for a brief 6.5-kHz signal were measured in the presence of a notched-noise masker over a range of masker levels. The masker was either gated with the signal (overshoot condition) or was of long duration with the signal temporally centered in it. At mid masker levels, thresholds in the gated condition were substantially higher than in the long-masker condition (overshoot). The overall amount of overshoot and the variation in overshoot as a function of masker level support the view that, even at high frequencies, the overshoot effect is dominated by off-frequency masker components. Pure-tone intensity discrimination tasks were then performed in quiet, and in the presence of the same notched noise in both gated and long-duration noise conditions. It was found that the temporal characteristics of the notched noise and not, as previously thought, the pedestal determined whether or not a severe departure from Weber’s law in intensity discrimination was observed. The severe departure from Weber’s law was found only in an overshoot condition and then only when the pedestal was presented near masked threshold. This is not in accordance with a previous explanation of the severe departure in terms of two populations of auditory nerve fibers (high- and low-threshold fibers). A further experiment measured psychometric functions for the detection of the 6.5-kHz signal in both gated and long-duration notched noise. It was found that the psychometric function was markedly shallower in an overshoot condition (mid-level gated masker) than in the other conditions. These findings are consistent with a new theory, explaining the severe departure from Weber’s law in terms of both the variance in the internal representation of stimuli in an overshoot condition, and the loudness of partially masked signals.

Effects of bilateral olivocochlear lesions on pure tone intensity discrimination in cats

The effects of olivocochlear efferent lesions on intensity discrimination were examined in five cats. Cats were trained with food reinforcement to signal the detection of a change in the intensity of a pure tone by releasing a response lever. Intensity cues were conveyed by 1- and 8-kHz tone bursts in quiet and in the presence of continuous broadband noise. After the collection of baseline behavioral data, the olivocochlear bundle (OCB) was sectioned with bilateral knife cuts on the floor of the IVth ventricle. The completeness of OCB lesions was evaluated with cochlear acetylcholinesterase staining procedures. Although intensity discrimination was not negatively affected by OCB lesions when tests were conducted in quiet, performance deficits were noted when intensity discrimination was measured in the presence of noise. These data suggest that olivocochlear feedback may play an important role in the auditory processing of acoustic signals in noise backgrounds. Behavioral results will be discussed in terms of electrophysiological measures of intensity encoding. [Work supported by NIDCD Grant No. DC00979 and the W. M. Keck Foundation.]

Effects of vestibular neurectomy on intensity discrimination and speech perception in noise

Olivocochlear efferents are assumed to be severed during vestibular neurectomy in subjects with severe vertigo. Effects of vestibular neurectomy on pure-tone intensity discrimination and speech perception in noise were examined in six subjects by comparing performance between the surgery ear and the nonsurgery ear, and when available, between the pre- and post-operative conditions. Five of the six subjects had normal or near normal pure-tone average thresholds (<30 dB HL). Broadband white noise was used as in intensity discrimination, and speech spectral-shaped noise was used in speech reception threshold measurements. Both types of noise were presented binaurally at several different levels, whereas the tone or speech was presented monaurally and its level was varied adaptively according to the subject’s response. Preliminary results show that (1) loudness dynamic range is not affected by the surgery, (2) intensity and speech perception in noise significantly worsen after the surgery in some subjects but not others. The variability of the results may be due to the fact that not all efferents are severed in every subject during vestibular neurectomy. An objective measure of the efferent nerve survival after vestibular neurectomy in these subjects is needed to further understand perceptual function of the cochlear efferent pathway. [Work supported by NIH-BRSG.]

Recovery from prior stimulation II: Effects upon intensity discrimination

We obtained just-noticeable differences (inds) for the intensity of pure tones following a forward masker. The masker was a 100-ms burst of narrow-band noise centered at 1000 Hz presented at 90 dB SPL; the pure-tone signal was at 1000 Hz and was 25 ms in duration. The masker-signal delay was 100 ms. Under these conditions, there is no threshold shift for the detection of the pure-tone signal following the forward masker. In contrast with the absence of a forward-masker effect upon detection thresholds, unusually large midlevel (40–60 dB SPL) jnds were observed. These large midlevel jnds were measured as a function of signal delay, revealing that they are not completely recovered to the normal (unmasked) values by 400 ms. We interpret these data as a consequence of the slower recovery of low-spontaneous rate, high-threshold neurons following prior stimulation (Relkin and Doucet, 1990). These experiments may therefore provide psychophysical evidence that the low-spontaneous rate, high-threshold neurons are a necessary physiological component in the coding of the large dynamic range for intensity. In addition, the present data provide evidence that the assumption that the effect of forward masking is limited to 100–200 ms is inappropriate, as this recovery time does not necessarily apply to suprathreshold tasks.

Interrelations Between the Auditory, the Visual and the Lateral Line Systems of Teleosts; a Mini-Review of Modelling Sensory Capabilities

Models are proposed, which allow the quality of performance of the auditory, visual and mechanosensory lateral line systems of 63 teleost species to be calculated. These systems are particularly suitable for remote detection of objects. The general capability of each system is expressed as an index, which is evaluated in relation to habitat and behaviour. The index of the lateral line canal system, LI, is mainly based on anatomical characteristics. Species with many superficial neuromasts generally have low LIs and appear to prefer quiet waters. The hearing index, HI, is based on the audiogram, the intensity discrimination threshold and the psychophysical tuning curve. It expresses the number of distinguishable pure tone-intensity combinations. Highest HIS are found among species living in shallow, mostly fresh waters with soft bottoms. Low and moderate HIS are related to noisy habitats. Excellent hearing is found only in species with Weberian ossicles or other structures to improve the swimbladder-ear coupling. The visual index, VI, is based upon the focal length of the eye and characteristics of the two principal retinorecipient tectal layers. The volume of these layers is proportional to the retinal surface area, irrespective of species and size. VI is in broad agreement with published data on the psychophysical minimum resolvable angle. High VIs are found among pelagic, diurnal species living in clear waters and vice versa. Well-developed canal lateral line organs seldom go together with very good hearing, but a high HI is often accompanied by large numbers of superficial neuromasts. Poor hearing is often compensated for by good vision, and vice versa. Species with a high VI are mostly predators.

Pure-tone intensity discrimination in hearing-impaired and normal-hearing listeners

Intensity jnd's for 500-ms tones were obtained from five cochlear-impaired and three normal-hearing subjects. The jnd-level functions, from threshold to 97 dB SPL, were measured at five test frequencies, in quiet and in high-pass noise. The “near-miss” to Weber's law was observed from normals in quiet, from two subjects with flat losses, and from regions of normal threshold in three subjects with high-frequency loss. In the same three ears, at frequencies just below and within the region of loss, jnd's conformed to Weber's law, as did the jnd's obtained in the presence of the noise for all subjects. These results are consistent with explanations of the near-miss that involve excitation at frequency regions well above the test frequency. At equal SLs, jnd's in quiet from impaired subjects were equal to, or larger than, jnd's from normals. At equal SLs, jnd's in quiet from hearing-loss subjects were sometimes smaller than normal, but were usually elevated by high-pass noise, thus implicating the near-miss. In some cases, however, jnd's at low SLs were still smaller in the noise, which may reflect the steeper rate-level functions seen in the auditory nerve in regions of cochlear loss [M. C. Liberman and N. Y.-S. Kiang, Hear. Res. 16, 75–90]. [Work supported by NINCDS Grant NS 12125.]

Loudness Scales from Loudness Processes: A Multivariate Approach

Five subjects were required to judge the loudness of pure tones that varied in intensity and duration (Experiment 1), in intensity and frequency (Experiment 2), or in duration and frequency (Experiment 3). Results of all three experiments were consistent with the respective models of sensory integration expected to underlie the various judgmental tasks (multiplicative for the first experiment, unidimensional for the latter two). Despite the use of common stimulus values across experiments and instructions to judge solely loudness, different loudness scales emerged. This outcome supports a task dependent, multirepresentative scheme for loudness.

Intensity discrimination at three frequencies by means of pulsed‐ and continuous‐tone paradigms

Difference limens (DL's) for the intensity of pure tones were measured with 2AFC pulsed‐tone and continuous‐tone paradigms at 500, 2000, and 6000 Hz across a broad range of sensation levels (SL's). In the pulsed‐tone experiments, the pedestal was gated simultaneously with the increments, whereas, in the continuous‐tone experiments the pedestal began 400 ms before the first observation interval, and continued throughout the trial until 400 ms after the termination of the second observation interval. The DL's obtained on five normal subjects were lower for the continuous‐paradigm than for the pulsed‐tone conditions for all test frequencies and SL's. The difference agrees with physiological results showing that the single‐unit neural response to an increment is independent of whether the increment is presented to fibers that are adapted (continous‐tone experiment) or unadapted (pulsed‐tone) experiment [Smith and Zwislocki, Biol. Cyber. (1975)] and also with the argument that the pulsed‐tone paradigm involves...

Loudness of Pure Tones at Low and Infrasonic Frequencies

Contours of equal loudness were determined in the frequency range 2–63 Hz and the loudness range 20–100 phon. The loudness curves run almost parallel in the infrasonic frequency range and much closer than in the audio region. Infrasound only a few dB above the hearing threshold will therefore seem loud and possibly annoying. The subjects were 20 normal hearing students aged between 18 and 25, and the psychometric method was based on maximum-likelihood estimation of psychometric functions.