Reference Tone Research Articles

Subjective loudness level measurements and equal loudness contours in a bottlenose dolphin (Tursiops truncatus)

Loudness level measurements in human listeners are straightforward; however, it is difficult to convey the concepts of loudness matching or loudness comparison to (non-human) animals. For this reason, prior studies have relied upon objective measurements, such as response latency, to estimate equal loudness contours in animals. In this study, a bottlenose dolphin was trained to perform a loudness comparison test, where the listener indicates which of two sequential tones is louder. To enable reward of the dolphin, most trials featured tones with identical or similar frequencies, but relatively large sound pressure level differences, so that the loudness relationship was known. A relatively small percentage of trials were "probe" trials, with tone pairs whose loudness relationship was not known. Responses to the probe trials were used to construct psychometric functions describing the loudness relationship between a tone at a particular frequency and sound pressure level and that of a reference tone at 10 kHz with a sound pressure level of 90, 105, or 115 dB re 1 μPa. The loudness relationships were then used to construct equal loudness contours and auditory weighting functions that can be used to predict the frequency-dependent effects of noise on odontocetes.

Responses to deviants are modulated by subthreshold variability of the standard

Auditory mechanisms automatically detect both basic features of sounds and the rules governing their presentation. In the oddball paradigm, the auditory system detects the sameness (or no-variability) rule when the same reference tone is consistently repeated. We used two oddball protocols, the classical one with a fixed reference and a modified one with a jittered reference, to determine whether the auditory system can detect subthreshold violations of sameness. We found that the response to the repeated standard was not modified by the small jitter. However, the response to the frequency oddball was smaller under the jittered protocol, indicating hypersensitivity to sameness. The sensitivity to jitter was largest when the oddball deviated by 8%, was smaller for 40%, and disappeared at 100% deviation, indicating that sensitivity to sameness is context dependent; namely, it is scaled with respect to the overall range of stimuli.

Vision and Audition Do Not Share Attentional Resources in Sustained Tasks

Our perceptual capacities are limited by attentional resources. One important question is whether these resources are allocated separately to each sense or shared between them. We addressed this issue by asking subjects to perform a double task, either in the same modality or in different modalities (vision and audition). The primary task was a multiple object-tracking task (Pylyshyn and Storm, 1988), in which observers were required to track between 2 and 5 dots for 4 s. Concurrently, they were required to identify either which out of three gratings spaced over the interval differed in contrast or, in the auditory version of the same task, which tone differed in frequency relative to the two reference tones. The results show that while the concurrent visual contrast discrimination reduced tracking ability by about 0.7 d′, the concurrent auditory task had virtually no effect. This confirms previous reports that vision and audition use separate attentional resources, consistent with fMRI findings of attentional effects as early as V1 and A1. The results have clear implications for effective design of instrumentation and forms of audio–visual communication devices.

Enhancement of Speech-Relevant Auditory Acuity in Absolute Pitch Possessors

Absolute pitch (AP) is the ability to identify the frequency or musical name of a specific tone, or to identify a tone without comparing it with any objective reference tone. While AP has recently been shown to be associated with morphological changes and neurophysiological adaptations in the planum temporale, a cortical area in the brain involved in speech perception processes, no behavioral evidence of speech-relevant auditory acuity in any AP possessors has hitherto been reported. In order to seek such evidence, in the present study, 15 professional musicians with AP and 14 without AP, all of whom had acquired Japanese as their first language, were asked to identify isolated Japanese syllables as quickly as possible after these syllables were presented auditorily. When the mean latency to the syllable identification was compared, it was significantly shorter in AP possessors than in non-AP possessors whether the presented syllables were those used as Japanese labels representing the 7 tones constituting an octave or not. The latency to hear the stimuli per se did not differ according to whether the participants were AP possessors or not. The results indicate the possibility that possessing AP provides one with extraordinarily enhanced acuity to individual syllables per se as fundamental units of a segmented word in the speech stream.

The effects of ear of stimulus presentation on pitch discrimination abilities of young adult females.

Previous research has examined various factors that influence pitch discrimination abilities in normal‐hearing listeners [Deutsch (1970); (1978)], including the influence of spatial location of input stimuli. Separating the input location of interference tones from the initial (reference) and final (comparison) tones leads to better pitch discrimination accuracy (PDA) than when all tones are presented to the same ear, but the effects of the relationships between these three tone types have not been explored. This study examined the impact of ear of stimulation in 20 conditions: 5 containing no interference and 15 containing 4 interference tones. Twenty‐four non‐musician females (age 19–30) with normal hearing participated. Results showed that performance was significantly better when (a) no interference was present, (b) the comparison tone was presented contralaterally to reference and interference tones, (c) the comparison tone was presented to the left ear, and (d) the reference and comparison tones wer...

Explicit Auditory Discrimination Improves During the Visual Attentional Blink

Gating of sensory information is an elementary function, necessary for survival. In a series of studies, we investigated how sensory modalities interact in this process. We previously probed implicit allocation of multisensory attention during the Attentional Blink (AB), a failure to report a second target closely following first target detection (Haroush et al., ECVP 2007). In that study, we examined AB effects on the event-related Mismatch Negativity (MMN), which is ‘automatically’ elicited upon appearance of a deviant within a sequence of sounds. We found that MMN amplitude surprisingly increased during the AB, presumably underlying enhanced implicit auditory change detection processes. Here, we examined whether and how this effect translates into behavior, testing explicit auditory discrimination during a visual AB. Subjects were asked to identify two visual targets (T1&T2) embedded within a rapid distractor stimulus stream, and simultaneously perform an auditory discrimination task in a two-alternative-forced-choice, 2down-1up staircase paradigm. The first sound appeared at the beginning of the trial, (before visual T1), and the second simultaneously with visual T2, at variable SOAs. Three auditory protocol blocks were used with/without fixed reference tones to distinguish sensory classification from working-memory (WM) dependent discrimination (Nahum et al., 2009). When auditory discrimination was WM dependent, auditory performance during visual attentional blink trials significantly improved compared to trials where both visual targets were correctly reported. In contrast, sensory classification alone did not benefit from the visual AB, presumably because of its independence of WM. We conclude that attention-controlled WM resources that could not be used by the visual system during the AB are freed to be employed by the auditory system. Notably, this attention allocation is evident despite the additional resources taxed by task-switching. These results have implications for current theories of multiple information processing bottlenecks.

Audiological outcome of the pull‐back technique in cochlear implantees

The distance of the cochlear implant electrode contacts to the modiolus can be reduced by a surgical technique called "pull-back." This procedure changes the location of the fully inserted electrode array by moving the electrode out of the cochlea until the first silicon ring is visible in the cochleostomy. This leads to a more focused stimulation, which in turn could possibly improve hearing performance. The objective of the present study was to investigate the influence of the pull-back technique on frequency difference limens (FDL) and speech perception. Double-blind trial. Twelve pull-back and 12 matched controls (matched by age, gender, duration of deafness, and duration of implant use) were used. Twenty-four patients were implanted with the Nucleus-24 Contour Advance array. In 12 patients the pull-back technique was used and in 12 matched controls a standard insertion technique was applied. Twelve months after the initial stimulation speech perception, spread of neuronal excitation (SOE) at electrodes 5, 10, and 15; and FDLs at 1, 2, and 4 kHz were measured. There was no significant difference of speech perception performance between the two groups. However, the mean FDL for the 4 kHz reference tone was significantly lower in the pull-back group compared to the controls. The SOE was significantly reduced at basal, middle, and apical electrodes in the electrode pull-back group. The pull-back technique seems to have its greatest effect on perimodiolar position in the basal regions of the cochlea. Therefore, it is most likely to observe improved FDL in the 4 kHz region. Current speech recognition tests do not reflect the lower FDL.

From Comparison to Classification: A Cortical Tool for Boosting Perception

Humans are much better in relative than in absolute judgments. This common assertion is based on findings that discrimination thresholds are much lower when measured with methods that allow interstimuli comparisons than when measured with methods that require classification of one stimulus at a time and are hence sensitive to memory load. We now challenged this notion by measuring discrimination thresholds and evoked potentials while listeners performed a two-tone frequency discrimination task. We tested various protocols that differed in the pattern of cross-trial tone repetition. We found that best performance was achieved only when listeners effectively used cross-trial repetition to avoid interstimulus comparisons with the repeated reference tone. Instead, they classified one tone, the nonreference tone, as either high or low by comparing it with a recently formed internal reference. Listeners were not aware of the switch from interstimulus comparison to classification. Its successful use was revealed by the conjunction of improved behavioral performance and an event-related potential component (P3), indicating an implicit perceptual decision, which followed the nonreference tone in each trial. Interestingly, tone repetition itself did not suffice for the switch, implying that the bottleneck to discrimination does not reside at the lower, sensory stage. Rather, the temporal consistency of repetition was important, suggesting the involvement of higher-level mechanisms with longer time constants. These findings suggest that classification is based on more automatic and accurate mechanisms than interstimulus comparisons and that the ability to effectively use them depends on a dynamic interplay between higher- and lower-level cortical mechanisms.

The representation of pitch in auditory imagery: Evidence from S-R compatibility and distance effects

In three experiments we explored the nature of representations constructed during the perception and imagination of pitch. We employed a same–different task to eliminate the influence of nonauditory information and to minimise use of cognitive strategies on auditory imagery. A reference tone of frequency 1000, 1500, or 2000 Hz, or an imagined tone of a pitch indicated by a visual cue, was followed by a comparison tone (1000, 1500, or 2000 Hz) to which either a speeded same or different response was required. In separate experiments, same–different judgements were mapped to vertically (Experiments 1 and 2) and horizontally arranged responses (Experiment 3). Judgements of tones closer in pitch yielded longer reaction times and higher error rates than more distant tones, indicating a pitch distance effect for perceptual and imagery tasks alike. In addition, in the imagery task, same–different responses were faster when low-pitched tones demanded a bottom or left key response and high-pitched tones a top or right response than vice versa, suggesting that pitch is coded spatially. Together, these behavioural effects support the assumption that both perceived and imagined pitch are translated into an analogical representation in the spatial domain.

Frequency discrimination in rats measured with tone-step stimuli and discrete pure tones

Two modified go/no-go tasks are compared for the measurement of frequency discrimination in albino rats. The first task required detection of an instantaneous, phase-matched frequency change, called a “tone-step,” within a continuous reference tone. The more traditional second task required detection of a frequency change between repetitions of a reference sequence of repeating discrete tones. For each task frequency difference limens were measured over a range of reference frequencies from 2.31 to 27.7 kHz at 60 dB sound pressure level, with both upward and downward frequency shifts. All 24 subjects quickly learned the “tone-step” task to criterion, but only 13 could also learn the discrete tone task. Subjects’ performance at either task generally improved with increasing reference frequency, and in both tasks upward frequency change thresholds were significantly higher than thresholds for downward changes. Overall mean Weber ratios were 1.73 ± 0.27% for the “tone-step” task and 2.76 ± 0.29% for the discrete tone task. However, subjects’ performance on the “tone-step” task was not correlated with subsequent performance on the discrete tone task. We suggest that the lack of correspondence between tasks might be due to frequency discrimination processes interacting with short-term memory traces during inter-tone intervals in the discrete tone task.

Optical arbitrary waveform characterization via dual-quadrature spectral shearing interferometry

We demonstrate a new dual-quadrature spectral shearing interferometry technique appropriate for spectral phase characterization of arbitrary optical waveforms generated by line-by-line shaping of high-repetition- rate (approximately 10 GHz) optical frequency combs. Spectral shearing interferograms are generated through sum-frequency mixing of the frequency comb field with a pair of reference tones generated via intensity modulation of a continuous-wave laser. Although related to the well known SPIDER method, our approach relaxes spectral resolution requirements and operates in a collinear interaction geometry compatible with the use of high sensitivity, aperiodically poled lithium niobate nonlinear waveguide devices.

The Intensity–Pitch Relation Revisited: Monopolar Versus Bipolar Cochlear Stimulation

The very high speech perception scores now being achieved with cochlear implants have led to demands for similar levels of achievement in music perception and perception in noisy environments. One of the crucial factors in these fields is pitch perception. The aim of the present study was to investigate the extent to which pitch perception is influenced by the intensity of the stimulus, through the use of different stimulation modes (monopolar, bipolar) and different electrodes (lateral and perimodiolar). Sixteen postlingually deafened patients with an average implant use of 3.1 years were included in this study. All patients were using a Cochlear (CI24M, CI24R, CI24RE) cochlear implant. Subjects were asked to compare the pitch of an intensity-constant reference tone with the pitch of a test tone of varying intensity. The test was repeated for apical, mediocochlear, and basal channel locations, and also for monopolar and bipolar stimulation. It was found that in monopolar stimulation 87.5% and in bipolar stimulation 85.7% of the patients perceived a clear pitch change with changing intensity of the stimulus (Spearman correlation coefficients r < -0.3 or r > 0.3, respectively). A total of 73.1% of these patients perceived lower pitches with increasing intensity, 26.9% reported the opposite effect. No statistically significant difference in the intensity-pitch correlation could be found between mono- and bipolar stimulation. Neither the mean dynamic range nor the type of electrode used was found to be related to the correlation coefficient. Although the majority of today's cochlear implant recipients perform well and the intensity-pitch relation in cochlear implant recipients is still poorly understood, rising demands on speech-coding strategies may soon make a compensation of the pitch shifts desirable. Although the results of our study tend to argue against a peripheral mechanism, the exact origin of this phenomenon remains unclear.

Eigenvalue equalization filtered-x algorithm for the multichannel active noise control of stationary and nonstationary signals

The FXLMS algorithm, which is extensively used in active noise control, exhibits frequency dependent convergence behavior. This leads to degraded performance for time-varying and multiple frequency signals. A new algorithm called the eigenvalue equalization filtered-x least mean squares (EE-FXLMS) has been developed to overcome this limitation without increasing the computational burden of the controller. The algorithm is easily implemented for either single or multichannel control. The magnitude coefficients of the secondary path transfer function estimate are altered while preserving the phase. For a reference signal that has the same magnitude at all frequencies, the secondary path estimate is given a flat response over frequency. For a reference signal that contains tonal components of unequal magnitudes, the magnitude coefficients of the secondary path are adjusted to be the inverse magnitude of the reference tones. Both modifications reduce the variation in the eigenvalues of the filtered-x autocorrelation matrix and lead to increased performance. Experimental results show that the EE-FXLMS algorithm provides 3.5-4.4 dB additional attenuation at the error sensor compared to normal FXLMS control. The EE-FXLMS algorithm's convergence rate at individual frequencies is faster and more uniform than the normal FXLMS algorithm with several second improvement being seen in some cases.

The neural networks involved in pitch labeling of absolute pitch musicians

Investigating the neural substrates of auditory processing of absolute pitch musicians has relevance for understanding the capabilities of the human brain for plasticity. Electroencephalography was used to examine the N1 of auditory-evoked potentials from absolute pitch musicians, nonabsolute pitch musicians, and nonmusicians during tone labeling tasks with and without presentation of a reference tone. Source localization using low-resolution electromagnetic tomography revealed that when labeling tones without a reference, absolute pitch musicians generated greater activity than nonabsolute pitch musicians in the left and right hemispheres. This suggests that when required to label tones without an external reference, absolute pitch musicians have the ability to recruit a greater network than nonabsolute pitch musicians or nonmusicians.

Clinical application of long-term intensity and pitch matches in fluctuating low-frequency hearing loss

The purpose of this study was to measure changes in intensity and pitch matches to better assess disease activity in fluctuating hearing loss. Long-term suprathreshold audiometry was carried out at home on a subject with a unilateral fluctuating low-frequency hearing loss during a period when the subject demonstrated no symptoms and a period when the subject reported hearing loss, aural pressure, and tinnitus. Daily measurements of binaural intensity and pitch matches were made. Day-to-day fluctuations were clearly accentuated during the period when the subject experienced symptoms. Specifically, deviations from the reference tone were only observed for binaural pitch matches at 1 kHz during the period without symptoms; however, highly fluctuating binaural intensity and pitch matches were observed at 0.25 kHz during the period with symptoms. These fluctuations were not observed in a normal-hearing group. The results suggest that long-term measurements of binaural intensity and pitch matches can be used to monitor disease activity in fluctuating low-frequency hearing loss.

Long-term measurement of binaural intensity and pitch matches. II. Fluctuating low-frequency hearing loss

Thirteen subjects made consecutive long-term recordings of binaural intensity and pitch matches in their homes using portable equipment to assess hearing fluctuations. Two groups of subjects were used; one with monaural fluctuating low-frequency hearing loss (FLFHL) without vertigo, and one with monaural Ménière's disease (i.e. FLFHL with vertigo). The subjects measured binaural pitch matches using a 0.25- or 1-kHz reference tone presented at 60 dB SPL to one ear, and a loudness-matched test tone of adjustable frequency presented to the other ear during one to several weeks. Their results were compared to those previously obtained from ten normal-hearing subjects. Both groups of subjects showed fluctuations in binaural intensity and pitch matches not seen in the normal-hearing group. We calculated the average day-to-day difference in matched intensity and frequency for each subject's test period as a measure of disease activity. This measure indicated that the group with Ménière's disease has a higher disease activity than the group with FLFHL without vertigo, and that both these groups of subjects had higher disease activity than normal-hearing subjects.

Long-term measurement of binaural intensity matches and pitch matches. I. Normal hearing

Changes in pitch perception and hearing thresholds over time have been observed in subjects with monaural fluctuating low-frequency hearing loss and Ménière's disease. Long-term suprathreshold audiometry and binaural pitch matches could provide information of these changes. Ten normal subjects were tested for stability of binaural intensity and pitch matches during 9–22 days in their homes with newly developed portable test equipment. Binaural pitch matches were measured using a 0.25- or 1-kHz reference tone presented at 60 dB SPL to one ear, and a loudness-matched test tone of adjustable frequency presented to the other ear. The results showed stable binaural intensity matches (individual inter-quartile ranges, IQRs, 1.2 to 5.7 dB), but binaural pitch matches varied greatly (IQR −0.6 to 5.3% at 0.25 kHz; IQR −1.6 to 7.9% at 1 kHz). Binaural pitch-matching was much better in subjects who could define pitch precisely during monaural pitch matching. It was concluded that in future long-term evaluations of patients with fluctuating inner-ear function, binaural intensity matches could be suitable for all, but binaural pitch matching only for selected patients.

Dichotomy and perceptual distortions in absolute pitch ability

Absolute pitch (AP) is the rare ability to identify the pitch of a tone without the aid of a reference tone. Understanding both the nature and genesis of AP can provide insights into neuroplasticity in the auditory system. We explored factors that may influence the accuracy of pitch perception in AP subjects both during the development of the trait and in later age. We used a Web-based survey and a pitch-labeling test to collect perceptual data from 2,213 individuals, 981 (44%) of whom proved to have extraordinary pitch-naming ability. The bimodal distribution in pitch-naming ability signifies AP as a distinct perceptual trait, with possible implications for its genetic basis. The wealth of these data has allowed us to uncover unsuspected note-naming irregularities suggestive of a "perceptual magnet" centered at the note "A." In addition, we document a gradual decline in pitch-naming accuracy with age, characterized by a perceptual shift in the "sharp" direction. These findings speak both to the process of acquisition of AP and to its stability.

A non spectrum-based visual display tool

A software program was developed to help musicians learn to tune just intonation intervals. A reference tone is played and Lissajous-like figures present a visual representation of the interval the musician’s sound makes with the reference tone. This approach is interesting, because the musician receives coordinated aural and visual feedback in real time, and this visual representation is produced without the overhead of doing a Fourier transform. Experiments that modify the figures to produce a usable representation of timbral differences, also using a non spectrum-based algorithm, are planned. [Work supported by the Veneklasen Foundation.]

Does Norwich’s entropy theory of perception produce equal-loudness contours?

Norwich & Wong [Percept. Psychophys. 59, 1997; derived backwards in JASA, 97, 1995] modeled loudness L versus intensity I by L(I,k,γ,Ith,n)=(k/2)ln(1+γ(I/Ith)n). They assumed Lth=L(Ith) and L=L−Lth, producing two loudnesses, L or L=L−Lth, giving L(Ith)=Lth or 0, and L(0)=0 or (−k/2)ln(1+γ), a negative. They took dL/dI, called it ΔL/ΔI, and rearranged it, giving ΔI/I(ΔL,k,γ,Ith,n). New terms S∞(ΔL,n,k) and S0(ΔL,n,γ,k) were introduced, thus γ=S∞/(S0−S∞). The result was ΔI/I in S∞, S0, and n, identical to an equation of Riesz (Phys. Rev., 31, 1928). Riesz’s empirical S∞, S0, and n provided γ’s and n’s for L(I)=L(I,k,γ,Ith,n)−(k/2)ln(1+γ). Assuming k was constant, Norwich & Wong equated L(I)’s for comparison and reference tones, generating equal‐loudness contours. The contours contradicted empirical ones; to adjust, they replaced Riesz’s n by Stevens’ Index, x. The present author curvefitted the Entropy Equation and Stevens’ Law to 37 loudness‐growth plots. k depended on maximum loudness as k=0.173Lmax1.41 n...