Effects of aspirin on distortion product fine structure: interpreted by the two-source model for distortion product otoacoustic emissions generation

Distortion product otoacoustic emission (DPOAE) fine structure is due to the interaction of two major components coming from different places in the cochlea. One component is generated from the region of maximal overlap of the traveling waves generated by the two primaries and is attributed to nonlinear distortion (nonlinear component). The other component arises predominantly from the tonotopic region of the distortion product and is attributed to linear coherent reflection (reflection component). Aspirin (salicylate) ototoxicity can cause reversible hearing loss and reduces otoacoustic emission generation in the cochlea. The two components are expected to be affected differentially by cochlear health. Changes in DPOAE fine structure were recorded longitudinally in three subjects before, during, and after aspirin consumption. Full data sets were analyzed for two subjects, but only partial data could be analyzed from the third subject. Resulting changes in the two components of DPOAE fine structure revealed variability among subjects and differential effects on the two components. For low-intensity primaries, both components were reduced with the reflection component being more vulnerable. For high-intensity primaries, the nonlinear component showed little or no change, but the reflection component was always reduced.     

Sources of variability in distortion product otoacoustic emissions

The goal of this study was to determine the extent to which the variability seen in distortion product otoacoustic emissions (DPOAEs), among ears with normal hearing, could be accounted for. Several factors were selected for investigation, including behavioral threshold, differences in middle-ear transmission characteristics either in the forward or the reverse direction, and differences in contributions from the distortion and reflection sources. These variables were assessed after optimizing stimulus parameters for individual ears at each frequency. A multiple-linear regression was performed to identify whether the selected variables, either individually or in combination, explained significant portions of variability in DPOAE responses. Behavioral threshold at the f(2) frequency and behavioral threshold squared at that same frequency explained the largest amount of variability in DPOAE level, compared to the other variables. The combined model explained a small, but significant, amount of variance in DPOAE level at five frequencies. A large amount of residual variability remained, even at frequencies where the model accounted for significant amounts of variance.     

Periodogram based tests for distortion product otoacoustic emissions

Distortion product otoacoustic emissions (DPOAEs) are an important nonbehavioral measure of cochlear function, which provides a close analogue of the behavioral pure-tone audiogram. DPOAEs are sinusoidal distortion products (DPs) produced by nonlinearities in the healthy cochlea. Detection of DPs is accomplished in the Fourier domain with a periodogram based test. The test compares the power in the DP periodogram bin to a noise estimate derived from a certain number of the surrounding bins. Statistical properties of this test to date have only been examined by constructing receiver operator characteristics curves derived from DPOAE measurements in normal and hearing impaired individuals. In this paper the null distribution of this order-statistic based test is explicitly derived, and via simulations intended to mimic the nonwhite features of real-ear noise measurements, the power of the test is demonstrated. These simulations demonstrate that a local F test is more powerful than this DPOAE test, with critical values that are easier to calculate. Although the power of both tests increase with an increasing number of bins, the improvement is negligible at around four bins. Since the power of both tests decrease at lower DP frequencies, it is not recommended to use a large number of bins.     

Developing standards for distortion product otoacoustic emission measurements

Characteristics of distortion product otoacoustic emission (DPOAE) measurements were investigated by comparing responses from two different emission measurement systems in 40 volunteers (78 ears) and making test-retest measurements of each system in 20 ears. For transformation of results between systems, it was shown that the minimum data set consisted of input-output (growth) functions obtained by stepping stimulus levels across a wide range, for each set of stimulus frequencies (1-8 kHz). Linear transformations were considered which involved either recalibration of the emission amplitude (vertical transformation) or of the stimulus levels (horizontal transformation). Horizontal transformations provided better agreement between growth functions from the two systems. For frequencies 4-8 kHz, the means of the horizontal shifts required ranged from 8 to 14 dB, clearly exceeding test-retest variability. The optimal horizontal transformation was derived and applied uniformly to all emission measurements; correlations r=0.81-0.89 were found between transformed emission amplitudes. To minimize the necessity for such transformations and to reduce the variability found both within and between systems, development of standardized equipment and methods is suggested for DPOAE measurements, including: (1) an optimized in-ear probe assembly; (2) use of intensity calibration; and (3) a focus on emission "threshold" measurement and analysis.     

Suppression of distortion product otoacoustic emissions and hearing threshold

A distortion product otoacoustic emission (DPOAE) suppression tuning curve (STC) shows the minimum level of suppressor tone that is required to reduce DPOAE level by a fixed amount, as a function of suppressor frequency. Several years ago, Mills [J. Acoust. Soc. Am. 103, 507-523 (1998)] derived, theoretically, an approximately linear relationship between the tip-to-tail suppressor level difference on a DPOAE STC, and the gain of the cochlear amplifier, defined as the maximum increase in the active over the passive basilar membrane (BM) response. In this paper, preliminary data from adult human subjects are presented that establish a correlation between this tip-to-tail DPOAE STC difference and the threshold of hearing, the latter measured at the frequency of the f2 primary tone. Assuming that both suppression and the DPOAE are by-products of active, nonlinear BM dynamics, the above result suggests that threshold elevation in mild levels of hearing loss may be attributed, in part, to a reduction of cochlear amplifier gain, which is detectable with the suppression paradigm.     

Modeling the temporal behavior of distortion product otoacoustic emissions

The temporal behavior of the 2f1-f2 distortion product otoacoustic emission is theoretically investigated for the case in which the lower frequency (f1) primary tone is on continuously, and the higher frequency (f2) one is pulsed on and off [e.g., Talmadge et al., J. Acoust. Soc. Am. 105, 275-292 (1999)]. On physical grounds, this behavior is expected to be characterized by various group delays associated with the propagation of (1) the f2 cochlear primary wave between the cochlear base and the primary distortion product generation region around x2 (the f2 tonotopic place), and (2) the 2f1-f2 cochlear distortion product (DP) waves between the cochlear base, the primary generation region of the distortion product, and the region around the 2f1-f2 tonotopic place where the generated apical moving DP wave is reflected toward the cochlear base [e.g., Talmadge et al., J. Acoust. Soc. Am. 104, 1517-1543 (1998)]. An approximate analytic expression is obtained for this behavior from the analysis of the Fourier integral representation of the auditory peripheral response to the primary stimuli. This expression also approximately describes the transient build-up of the components of different latencies in terms of the damping properties of the cochlear partition. It is shown that considerable caution must be applied in attempting to relate phase derivatives of the distortion product otoacoustic emissions for steady state stimuli and the physical time delays which are associated with the temporal behavior of a distortion product emission in the case of a pulsed primary.     

Low-frequency modulation of distortion product otoacoustic emissions in humans

Low-frequency modulation of distortion product otoacoustic emissions (DPOAEs) was measured from the human ears. In the frequency domain, increasing the bias tone level resulted in a suppression of the cubic difference tone (CDT) and an increase in the magnitudes of the modulation sidebands. Higher-frequency bias tones were more efficient in producing the suppression and modulation. Quasi-static modulation patterns were derived from measuring the CDT amplitude at the peaks and troughs of bias tones with various amplitudes. The asymmetric bell-shaped pattern resembled the absolute value of the third derivative of a nonlinear cochlear transducer function. Temporal modulation patterns were obtained from inverse FFT of the spectral contents around the DPOAE. The period modulation pattern, averaged over multiple bias tone cycles, showed two CDT peaks each correlated with the zero-crossings of the bias tone. The typical period modulation pattern varied and the two CDT peaks emerged with the reduction in bias tone level. The present study replicated the previous experimental results in gerbils. This noninvasive technique is capable of revealing the static position and dynamic motion of the cochlear partition. Moreover, the results of the present study suggest that this technique could potentially be applied in the differential diagnosis of cochlear pathologies.     

Spectral fine-structures of low-frequency modulated distortion product otoacoustic emissions

Biasing of the cochlear partition with a low-frequency tone can produce an amplitude modulation of distortion product otoacoustic emissions (DPOAEs) in gerbils. In the time domain, odd- versus even-order DPOAEs demonstrated different modulation patterns depending on the bias tone phase. In the frequency domain, multiple sidebands are presented on either side of each DPOAE component. These sidebands were located at harmonic multiples of the biasing frequency from the DPOAE component. For odd-order DPOAEs, sidebands at the even-multiples of the biasing frequency were enhanced, while for even-order DPOAEs, the sidebands at the odd-multiples were elevated. When a modulation in DPOAE magnitude was presented, the magnitudes of the sidebands were enhanced and even greater than the DPOAEs. The amplitudes of these sidebands varied with the levels of the bias tone and two primary tones. The results indicate that the maximal amplitude modulations of DPOAEs occur at a confined bias and primary level space. This can provide a guide for optimal selections of signal conditions for better recordings of low-frequency modulated DPOAEs in future research and applications. Spectral fine-structure and its unique relation to the DPOAE modulation pattern may be useful for direct acquisition of cochlear transducer nonlinearity from a simple spectral analysis.     

Higher order Ito product formula and generators of evolutions and flows

A simple combinatorial formula is found for the product of two iterated quantum stochastic integrals, and used to find conditions that such an integral represent a unitary-valued or^*-algebra homomorphism-valued process.     

畸变产物耳声发射信号的时域分离算法研究

针对在分离畸变产物耳声发射(Distortion Product Otoacoustic Emissions,DPOAE)不同产生源成分的过程中两成分之间存在交叉干扰的问题,建立了IFFT(Inverse Fast Fourier Transform,IFFT)结合时域窗的成分分离算法模型,结合模型进行了分离误差的分析,并在此基础上给出一种时间窗窗宽选择准则。根据IFFT后的时域波形,利用两成分主峰包络内的信号波形的矩心移动速率的快慢选择两成分之间的合适的分界点,将两成分分离开。对结合了该时间窗窗宽选择准则的时域成分分离算法进行了仿真,并对DPOAE实验数据进行了成分分离。仿真和实验结果表明,结合该窗宽选择准则的DPOAE时域分离算法可以成功地分离两个成分,且有效地减少了因两成分之间的交叉干扰引入的幅度和相位扰动。因此,结合该窗宽选择准则的DPOAE时域分离算法是有效的,可以提高分离不同产生源成分的准确性。     

畸变产物耳声发射信号的时域分离算法研究

针对在分离畸变产物耳声发射(Distortion Product Otoacoustic Emissions,DPOAE)不同产生源成分的过程中两成分之间存在交叉干扰的问题,建立了IFFT(Inverse Fast Fourier Transform,IFFT)结合时域窗的成分分离算法模型,结合模型进行了分离误差的分析,并在此基础上给出一种时间窗窗宽选择准则。根据IFFT后的时域波形,利用两成分主峰包络内的信号波形的矩心移动速率的快慢选择两成分之间的合适的分界点,将两成分分离开。对结合了该时间窗窗宽选择准则的时域成分分离算法进行了仿真,并对DPOAE实验数据进行了成分分离。仿真和实验结果表明,结合该窗宽选择准则的DPOAE时域分离算法可以成功地分离两个成分,且有效地减少了因两成分之间的交叉干扰引入的幅度和相位扰动。因此,结合该窗宽选择准则的DPOAE时域分离算法是有效的,可以提高分离不同产生源成分的准确性。     

Suppression of distortion product otoacoustic emissions in the anuran ear

When a two-tone stimulus is presented to the ear, so-called distortion product otoacoustic emissions (DPOAEs) are evoked. Adding an interference tone (IT) to these two DPOAE-evoking primaries affects normal DPOAE generation. The "effectiveness" of interference depends on the frequency of the IT in relation to the primary frequencies and this provides clues about the locus of emission generation within the inner ear. Here results are presented on the effects of ITs on DPOAEs thought to originate from the basilar papilla (BP) of a frog species. It is found that the IT always resulted in a reduction of the recorded DPOAE amplitude: DPOAE enhancement was not observed. Furthermore, iso-suppression curves (ISCs) exhibited two relative minima suggesting that the DPOAEs arise at different loci in the inner ear. These minima occurred at fixed frequencies, which coincided with those primary frequencies that resulted in maxima in DPOAE audiograms. The occurrence of two minima suggests that DPOAEs, which are presumed to originate exclusively from the BP, partially arise from the amphibian papilla as well. Finally, the finding that the minima in the ISCs are independent of the primary or DPOAE frequencies provides support for the notion that the BP functions as a single auditory filter.     

In search of quantum reality

Announcement

In search of quantum reality     

In search of non-exotic glueballs

Identification of a non-exotic glueball requires investigating the meson decuplet, including the \(q\bar q\) meson nonet and the glueball. The masses are a key factor in describing the decuplet. A particular feature of decuplet mixing is the possibility of hidden flavour being displaced between isosinglets. Some rules for searching for meson decuplets can be formulated.     

In search of scalar gluonium

We discuss a scalar meson coupled strongly to gluons. Radiative decays of the J/ψ are taken as a source of gluons so that our aim is to calculate Γ(J/ψ→σγ), where σ is the presumed scalar gluonium. We use QCD sum rules to find both 〈0|α_sG_μν^aG_μν^a|σ〉 (where G_μν^a is the gluon field strength tensor) and Γ(J/ψ→σγ) in terms of 〈0|α_sG_μν^aG_μν^a|σ〉. The final prediction for the width is expected to be valid within a factor of two and gives $\text{Γ(}\text{J}\text{/ψ→σγ→}\text{two pions in S-wave}\text{+ γ) ? 25}\text{eV for}\text{m}{}_{\mathrm{\sigma }}\text{= 700}\text{MeV}$. Non-perturbative QCD naturally explains the observed asymmetry between scalar and pseudoscalar states in the radiative decays of the J/ψ. Some general remarks on gluonium in QCD are made.     

Modeling and effect of distortion product generated by harmonic complex tones

To study deeply the effect of distortion product on auditory perception, a functional model is proposed to generate distortion products at frequencies below those of primary stimuli. The operations include calculating different power of the stimuli, low pass filtering, searching optimum weights, and summing the weighted signals across all filtering channels. The model uses simulate annealing and genetic algorithm to search the globally optimum weights. Moreover, this paper studies the effect of distortion products on pitch perception for unresolved harmonics based on the proposed model. Results find that distortion products could enhance the resolvability and temporal information of the harmonics. Thus, it is suggested to use background noise with appropriate sound levels to mask distortion products to reduce the effect on pitch perception.     

Nonlinear interactions that could explain distortion product interference response areas

Suppression and/or enhancement of third- and fifth-order distortion products by a third tone that can have a frequency more than an octave above and a level more than 40 dB below the primary tones have recently been measured by Martin et al. [Hear. Res. 136, 105-123 (1999)]. Contours of iso-suppression and iso-enhancement that are plotted as a function of third-tone frequency and level are called interference response areas. After ruling out order aliasing, two possible mechanisms for this effect have been developed, a harmonic mechanism and a catalyst mechanism. The harmonic mechanism produces distortion products by mixing a harmonic of one of the primary tones with the other primary tone. The catalyst mechanism produces distortion products by mixing one or more intermediate distortion products that are produced by the third tone with one or more of the input tones. The harmonic mechanism does not need a third tone and the catalyst mechanism does. Because the basilar membrane frequency response is predicted to affect each of these mechanisms differently, it is concluded that the catalyst mechanism will be dominant in the high-frequency regions of the cochlea and the harmonic mechanism will have significant strength in the low-frequency regions of the cochlea. The mechanisms are dependent on the existence of both even- and odd-order distortion, and significant even- and odd-order distortion have been measured in the experimental animals. Furthermore, the nonlinear part of the cochlear mechanical response must be well into saturation when input tones are 50 or more dB SPL.