Jan Hots

Increased intensity discrimination thresholds in tinnitus subjects with a normal audiogram

Recent auditory brain stem response measurements in tinnitus subjects with normal audiograms indicate the presence of hidden hearing loss that manifests as reduced neural output from the cochlea at high sound intensities, and results from mice suggest a link to deafferentation of auditory nerve fibers. As deafferentation would lead to deficits in hearing performance, the present study investigates whether tinnitus patients with normal hearing thresholds show impairment in intensity discrimination compared to an audiometrically matched control group. Intensity discrimination thresholds were significantly increased in the tinnitus frequency range, consistent with the hypothesis that auditory nerve fiber deafferentation is associated with tinnitus.

Loudness of subcritical sounds as a function of bandwidth, center frequency, and level

Level differences at equal loudness between band-pass noise and pure tones with a frequency equal to the center frequency of the noise were measured in normal-hearing listeners using a loudness matching procedure. The center frequencies were 750, 1500, and 3000 Hz and noise bandwidths from 5 to 1620 Hz were used. The level of the reference pure tone was 30, 50, or 70 dB. For all center frequencies and reference levels, the level at equal loudness was close to 0 dB for the narrowest bandwidth, increased with bandwidth for bandwidths smaller than the critical bandwidth, and decreased for bandwidths larger than the critical bandwidth. For bandwidths considerably larger than the critical bandwidth, the level difference was negative. The maximum positive level difference was measured for a bandwidth close to the critical bandwidth. This maximum level difference decreased with increasing reference level. A similar effect was found when the level differences were derived from data of an additional categorical loudness scaling experiment. The results indicate that the decrease of loudness at equal level with increasing subcritical bandwidth is a common property of the auditory system which is not taken into account in current loudness models.

Loudness of sounds with a subcritical bandwidth: A challenge to current loudness models?

Level differences at equal loudness were measured for bandpass noises centered at 1.5 kHz with bandwidths from 5 to 405 Hz and a 1.5-kHz pure tone. Irrespective of the reference (tone or 135-Hz wide noise), the data indicate a decrease in loudness with increasing bandwidth. This is at odds with the assumption of stationary loudness models that loudness for sounds with a subcritical bandwidth is determined by the intensity and center frequency only. It is also not in agreement with dynamic loudness models, which predict higher levels for a tone than for equally loud noises, i.e., the opposite effect.

Mid-bandwidth loudness depression in hearing-impaired listeners

The loudness of a bandpass-filtered noise depends on its bandwidth. For bandwidths larger than a critical bandwidth, loudness increases as the bandwidth increases, an effect commonly referred to as spectral loudness summation. For bandwidths smaller than the critical bandwidth, it was shown recently for normal-hearing listeners that loudness decreases as the bandwidth increases. This study investigated if listeners with a hearing impairment of primarily cochlear origin also showed this effect. Levels at equal loudness between a 1500-Hz pure-tone reference and noise-band targets centered at 1500 Hz were measured for bandwidths in the range from 15 to 1620 Hz. The reference level was adjusted individually on the basis of the audiogram. The average level difference at equal loudness increased from 0 dB at 15 Hz up to a maximum of about 4 dB at 810 Hz. Thus, the mid-bandwidth loudness depression is also observed for hearing-impaired listeners.

On the Pitch Strength of Bandpass Noise in Normal-Hearing and Hearing-Impaired Listeners

The psychoacoustic measure pitch strength describes the strength of the tonal sensation evoked by a sound on a scale from weak to strong. For normal-hearing listeners, it was shown in the literature that pitch strength of bandpass noise (relative to the pitch strength of a sinusoid at its center frequency) decreases with increasing bandwidth. This decrease also depends on the center frequency. These effects were often attributed to the frequency selectivity of the auditory system. The present study investigated the relative pitch strength of bandpass noise in hearing-impaired listeners and for comparison in a normal-hearing control group. For the normal-hearing listeners, pitch strength was measured at sound pressure levels of 30 and 70 dB SPL for bandwidths between 5 and 1620 Hz and center frequencies of 375, 750, and 1500 Hz. In addition, two ways of generating the stimuli (filtering in frequency or time domain) were used to compare the data with previous results. Apart from the known effect of center frequency on the change of relative pitch strength with increasing bandwidth, stimulus generation also had a significant influence on the results. Relative pitch strength of bandpass noise in hearing-impaired listeners was measured for bandwidths from 5 to 1620 Hz; the center frequency was 1500 Hz. Compared with the corresponding results of the normal hearing, relative pitch strength was altered in the hearing-impaired listeners. These alterations, however, could not be explained by altered spectral processing in the damaged cochlea alone.

Evaluation of a model of temporal weights in loudness judgments

The onset of a sound receives a higher weight than later portions in time when its loudness is assessed, an effect commonly referred to as primacy effect. It is investigated if this effect can be predicted on the basis of an exponentially decaying function where the weight assigned to a temporal portion of a sound is the integral of this function over the segment duration. To test this model, temporal loudness weights were measured for sounds with different segment durations and total durations. The model successfully predicted essential aspects of the data.

Temporal weights in the perception of sound intensity: Effects of sound duration and number of temporal segments

Loudness is a fundamental aspect of auditory perception that is closely related to the physical level of the sound. However, it has been demonstrated that, in contrast to a sound level meter, human listeners do not weight all temporal segments of a sound equally. Instead, the beginning of a sound is more important for loudness estimation than later temporal portions. The present study investigates the mechanism underlying this primacy effect by varying the number of equal-duration temporal segments (5 and 20) and the total duration of the sound (1.0 to 10.0 s) in a factorial design. Pronounced primacy effects were observed for all 20-segment sounds. The temporal weights for the five-segment sounds are similar to those for the 20-segment sounds when the weights of the segments covering the same temporal range as a segment of the five-segment sounds are averaged. The primacy effect can be described by an exponential decay function with a time constant of about 200 ms. Thus, the temporal weight assigned to a specific temporal portion of a sound is determined by the time delay between sound onset and segment onset rather than by the number of segments or the total duration of the sound.

Can partial loudness of the tonal content be the basis for tone adjustments

Environmental sounds containing tonal components are more annoying than those without audible tonal components. This is considered in several standards addressing the assessment of noise immissions. These standards have in common that the strength of the tonal component, referred to as tonality, tonalness, or magnitude of tonal content is taken as the level of the prominent audible tone relative to the surrounding background noise. Based on this magnitude of tonal content, some standards add tone adjustments to the measured sound levels to account for the reduced acceptance of a sound with audible tonal components. On the basis of experimental data and model predictions, the present study shows that the magnitude of the tonal content is better characterized by its partial loudness than by the signal-to-noise ratio of the prominent tonal component. Partial loudness of the tonal component may be considered in future standards as a basis for the assessment of the annoyance of the tonal content of a sound and...

Tone adjustments, or how an added tone makes a noise less pleasant

Several technical sounds contain tonal components which usually arise from rotating parts. Typical examples are sounds originating from turbines or electric engines. These sounds are commonly less pleasant than equal-level sounds without tonal components. To consider this effect on noise pollution, several standards include sections dedicated to tonal components. The standards have in common that they estimate the magnitude of the tones relative to the noise (e.g., tone-to-noise ratio, prominence ratio). Some standards include a second step where a few decibles are added to the measured sound levels, referred to as tone adjustment, to account for the reduction in pleasantness if tonal components are present. The aim of the present study was to measure the tone adjustment. First, the individual masked thresholds of three tonal components were determined. Then, the tonal components were added to the noise at three different levels above the individual masked threshold and a noise alone was adjusted in an ad...

On the influence of sensorineural hearing loss on the pitch strength of bandpass noise

In the perception of environmental noises and in the field of speech and music, tonality plays a crucial role. A tonal character can help the listeners to identify the sound source. However, environmental noises with a tonal character are also considered as especially annoying sounds. The psychoacoustic measure “pitch strength” describes the strength of the tonal sensation evoked by the sound on a scale from weak to strong. For normal-hearing listeners, it was shown in the literature that the pitch strength of bandpass noises decreased with increasing bandwidth when the center frequency was fixed and increased with increasing center frequency when the noise bandwidth was fixed. These results are presumably linked to the frequency selectivity of the auditory system. Since cochlear damage leads to a pathological widening of the auditory filters in the inner ear, an altered perception of pitch strength seems possible. In our study, we investigated whether and to which extent pitch strength is influenced by c...