External Sounds Research Articles

Decreased Sound Tolerance and Tinnitus Retraining Therapy (TRT)

The main objective of Tinnitus Retraining Therapy (TRT) is habituation of activation of the autonomic nervous system, evoked by signals present in the auditory pathways. Sound therapy aims at decreasing the strength of these signals. The same systems in the brain are involved in tinnitus and decreased sound tolerance, and the same basic neurophysiological mechanisms are utilised for decreasing the tinnitusrelated neuronal activity and, in case of hyperacusis, abnormally enhanced activity induced by external sounds. The similarity of TRT treatment between tinnitus and misophonia is even closer, as in both situations the goal is to achieve extinction of functional connections between the auditory and the limbic and autonomic nervous systems. The increased gain within the auditory pathways that are presumably responsible for hyperacusis could enhance the tinnitus signal, thus it is possible to expect coexistence of tinnitus and hyperacusis, and the predisposition of hyperacusis patients to develop tinnitus. As such, for some patients tinnitus and hyperacusis may be considered the double manifestation of the same internal phenomenon.

Age, music, and driving performance: Detection of external warning sounds in vehicles.

The growing elderly population increases the number of older drivers. Driving requires detection of information against an acoustic background. Modern vehicles are designed to reduce external noises (including warning signals) and provide audio entertainment options that capture auditory attention. The present study investigated the effects of age on the detection of external vehicular warning sounds (car horn or police siren) in the presence of road noise and road noise combined with music. Older listeners required higher warning sound intensities in background noise relative to younger listeners. For both age groups, intensity for detecting acoustically similar stimuli (siren and music) was higher than for dissimilar (car horn and music). Music in vehicles potentially increases accident risk for older drivers and suggests the need for technology that will augment rather than attenuate external warning sounds. Safe and effective driving necessitates detection of auditory information embedded in a background of continuously changing sounds. Music is an ubiquitous contributor of such sounds (DeNora, 2000). As much as 91% of exposure to music occurs during transportation (Sloboda,1999;Sloboda,0'Neill, & Vivaldi, 2001). Several factors might influence the effects of music on driving performance. They include (a) variation in musical tone, rhythm, tempo, melody contour, timbre etc. (Bregman, 1990); (b) complexity of sounds and their organizational layout (Brodsky, 2002; Schreiner, 1998); and (c) age-related loss of the ability to hear high frequency sounds (Willott, 1991). The present study investigated the effects of age on the detection of warning sounds of vehicles {car horn or police siren) in the presence of road noise and road noise combined with music. In developed countries, the elderly segment of the population is projected to increase dramatically in the next 45 years, especially in the age categories of 60 years and above. Thus, it is imperative that the contribution of age-related sensory, perceptual, and cognitive losses to car accidents be understood (Botwinick, 1985; Caird, 2001). While much of the information used in driving is visual, auditory information also plays a role (Sivak, 1996). Because modern vehicles are replete with systems that either filter out external noises, provide for entertaining distractions, or require increased auditory attention (Solomon, 2000), it is important to assess how the detection of warning sounds changes with age. It is also important to determine the type of information that affects the ability of older drivers to detect and identify warning sounds. A listener's ability to detect a warning sound within background sounds depends upon acoustic characteristics. When the characteristics of the warning signal are similar to those of a distracter, the detection and identification ofthat signal are degraded. Performance is particularly likely to deteriorate in the presence of uncertain distracters and informational masking (Grose & Hall, 1996; Leek, & Watson, 1984; Neff, Dethlefs, & Jestead, 1993; Slawinski, Hartel, & Kline, 1993). Informational masking refers to the effects of presentation of many unpredicted sounds on detection on a target sound. It is associated with selective attention and cognition, and it plays an important role in the processing of auditory information (Alien & Wightman, 1995; Slawinski & Scharf, 1998). An increase in the intensity of background noise also adversely affects the detection of a warning sound, Usually, older as compared to younger drivers require a higher ratio of the intensity of the target sound to the background noise (Yost, 1994). The emotional interest of music can also decrease sensitivity to a warning sound (Kassam, 2002). Some information processing abilities decline with increasing age (e.g., Murphy, Craik, Li, & Schneider, 2000) though in the case of audition, much of this is due to declining sensory ability (Schneider, Daneman, Pichora-Fuller, 2002). …

Acoustic resonance analysis of gas mixtures

An acoustic device for continuously or intermittently determining the composition of gas mixtures. The acoustic device has an acoustic resonator with input and output transducers arranged to minimize the effect of external conditions. The device normally operates as a feedback oscillator with the oscillation frequency determined by the gas-filled resonator's natural frequency, providing a speed of sound measurement. The device is configured as two open ended parallel side by side adjacent one half wavelength tubes, each with sending and receiving transducers inserted through a tube wall at the midpoint of that tube. This forms a symmetric quarter wave resonator from each tube. The two sending transducers are operated out of phase, as are the two receiving transducers. The causes cancellation of external sounds, and of their influence on measurements. A small pressure relieved cap is preferably placed over the external surface of each transducer. This farther reduces radiated sound and makes the effective resonator length essentially independent of the gas mixture's acoustic impedance, allowing operation over a wide pressure range. A simple electronic circuit provides appropriate differential gain, amplitude control, and phase shift, achieving steady oscillation. Determination of gas mixtures is by computation from frequency and temperature measurements, with real gas corrections as necessary.

The Pathway for the Transmission of External Sounds into the Fetal Inner Ear

After at least 20 weeks gestation, the human fetus in utero is able to hear and respond to external and internal (maternal) sounds. The external sounds are attenuated by maternal tissues and fluids - higher frequencies by about 20 dB, and lower frequencies are only slightly reduced. The sounds in the amniotic fluid, which completely envelops the fetus, then reach the fetal inner ear by bone conduction. The sound pressure in the amniotic fluid induces skull vibrations which are transmitted directly into the contents of the cranial cavity (brain and CSF) and from there, presumably by fluid channels connecting them, into the cochlear fluids. A further stage of conductive attenuation is probably involved in this transmission. Since the fetus in utero receives oxygen by placental diffusion (less efficient than pulmonary diffusion), the fetal inner ear is hypoxic compared to that following birth (pulmonary oxygen diffusion). This leads to a reduction in the magnitude of the endocochlear potential, to a depression of cochlear transduction and amplification, and thus to an additional sensorineural component of threshold elevation in the fetus. Upon birth, these conductive and sensorineural attenuations are removed.

Middle ear influence on otoacoustic emissions. I: Noninvasive investigation of the human transmission apparatus and comparison with model results

Evoked otoacoustic emissions (EOAEs) are generated within the cochlea in response to external sounds, and they can be acoustically detected in the external auditory meatus after backward propagation through the middle ear. In addition to being used to probe the cochlear mechanisms, they are expected to be sensitive to minute changes in middle ear impedance. Systematic measurements of the changes in the vectorial components of EOAEs were carried out after various manipulations of the human middle ear in order to characterize the influence of stiffness and inertia of the stapes and tympanic-membrane systems. For this purpose, stapedius muscle contractions were elicited by high-level contralateral sound, controlled changes in middle ear pressure (range ±100 daPa) were produced and the tympanic membrane was loaded with water droplets. A computer model of the middle ear network was implemented using a standard lumped-element electric analog of the middle ear (Zwislocki’s model). Forward and backward transmission changes were simulated and model predictions were compared to experimental data. Apart from the case of positive middle ear pressures, a close qualitative correspondence was found between model and real-ear results. Each of the effects was characterized by a unique pattern of phase and magnitude changes as a function of frequency, in relation to the mechanical characteristics of the involved subsystem (i.e. stapes stiffness, tympanic-membrane stiffness or mass) and its resonance properties. Owing to their high sensitivity, EOAEs could be helpful for an accurate individual multifrequency analysis of middle ear impedance by comparisons under rest and test conditions.

Minor Media - Heterogenic Machines

Minor Media - Heterogenic Machines

Vestibular hypersensitivity to clicks is characteristic of the Tullio phenomenon

OBJECTIVESThe frequency of pathologically reduced click thresholds for vestibular activation was explored in patients with the Tullio phenomenon (sound induced vestibular activation).METHODSSeven patients (eight affected ears) with symptoms of oscillopsia...

What sounds reach fetuses: biological and nonbiological modeling of the transmission of pure tones.

In utero transmission of external and maternal sounds has been studied in pregnant women and in an animal model of human species, the sheep. These works, especially the most recent ones, suggest that local and environmental factors interfere in such a way that signals are attenuated in a complex manner as frequency increases. The present work investigated whether a plain rubber sphere which was filled with water could be considered as a reliable nonbiological model in a study describing the characteristics of sound transmission. A sweeping pure tone, presented externally, was measured inside the rubber sphere using a high signal-to-noise ratio experimental hydrophone. A paradigmatic three components curve was observed between 100 and 20,000 Hz. In the first component of the curve (low to midfrequencies between 100 and 1,000 Hz), the intensity of the inside signal remained stable. The second component of the curve was composed of higher frequencies with the inside pressure falling gradually, demonstrating attenuation of the external signal. The third component of the curve appeared above a critical frequency, the value of which depended on several model and environment parameters. In this component, a series of rapid peaks and drops of the inside high frequency pressure was observed, indicating the presence of resonance systems. Analyses were carried out on the effects of several acoustical parameters, including: the size of the sphere, the location of the hydrophone in the sphere, the distance between the signal source and the hydrophone, the location of the external reference microphone, and the acoustical structure of the environment. These parameters allowed for the definition of their respective roles in the in-utero transmission of external sounds. These data were then compared with measurements performed within a biological model--ewes--under close acoustical settings. The comparisons confirmed the validity of the measurements, suggesting that the model may be useful in studies of sound transmission in utero.

2f1-f2 distortion product otoacoustic emissions in White Leghorn chickens (Gallus domesticus): effects of frequency ratio and relative level.

The effects of primary tone frequency ratio (f2/f1 ratio) and relative level (L2/L1) on the amplitude of the cubic difference tone (CDT: 2f1-f2) distortion product otoacoustic emissions (DPOAEs) were investigated in adult White Leghorn chickens (Gallus domesticus). In experiment 1, 9 f2/f1 ratios ranging from 1.05 to 1.8 were investigated. Measurements were obtained from both ears of 4 chickens at 7 f1 frequencies ranging from 0.8 to 4.0 kHz. The primary tones were equal in level, and varied from 20 to 80 dB SPL. The mean CDT amplitude increased with increasing primary tone level once the measurement noise floor was exceeded. The input/ output functions assumed one of two shapes: one in which there was a systematic increase in DPOAE amplitude with increasing primary tone level, and the other in which there was a plateau in the input/output function near 65-70 dB SPL. At the highest primary tone level (80 dB SPL), there was a decrease in the CDT amplitude with increasing f2/f1 ratio. At high primary tone levels, the f2/f1 ratio which produced the largest CDT was 1.05 or 1.1, while at lower primary tone levels the largest CDT occurred at f2/f1 ratios of 1.2-1.3. In experiment 2, L2 was held constant at 70 dB SPL, and L1 varied from 50 to 80 dB SPL. For f1 frequencies of 0.8 and 3.2 kHz, there was an increase in the CDT amplitude with increasing L1, followed by an asymptote at higher levels. In contrast, for 1.6 and 2.0 kHz f1 frequencies, the amplitude increased, plateaued and then increased again at higher levels. Informal measurements suggest that spontaneous otoacoustic emissions (SOAEs) are rarely seen in chickens. However, a reliable SOAE was observed in 1 chicken, which could be suppressed by external sounds and anoxia.

A Possible Masking Effect of Tinnitus: Evaluation of CNV audiometry

To determine whether tinnitus has a masking effect similar to that of general external sounds, the hearing threshold shift when the tinnitus was changed by intravenous administration of lidocaine was measured by contingent negative variation (CNV) audiometry. In a preliminary study, the reliability of CNV audiometry was evaluated in 12 patients with tinnitus. The reproducibility of CNV audiometry was confirmed, based on repeated measurements of CNV audiometry at the tinnitus frequency. The threshold difference between CNV audiometry and pure tone audiometry was -0.76 +/- 1.35 dB, and a high statistical correlation between the threshold of CNV audiometry and pure tone audiometry was evident. The CNV threshold shift at tinnitus frequency after lidocaine injection was measured in 89 ears. In the tinnitus-decreased group, the CNV threshold decreased (4-6 dB) in 22% of cases; however, in the tinnitus-unchanged group, the CNV threshold was little changed. These findings suggest that tinnitus may have a masking effect as is the case with external sounds.

A Model of the Mechanism of Sound Production in Cicadas

ABSTRACT Dried cicada bodies of the species Cyclochila australasiae and model cicadas made from a miniature earphone driving a plastic cavity were used to study the acoustics of sound production in male cicadas. A model cicada with shape and dimensions similar to those of the abdomen of a male C. australasiae resonates at the natural song frequency of the species (4.3 kHz). The abdominal air sac of C. australasiae also resonates at frequencies close to the natural song frequency when excited by external sounds. In an atmosphere of chlorofluorocarbon (CFC) gas, the resonant frequency is lowered in keeping with the decrease in velocity of sound in the CFC gas. At the model’s resonant frequency, the driving earphone dissipates more electrical power with the cavity attached than without the cavity. The cavity of the model cicada acts as a narrow-band acoustic acceptance filter, tuned to the natural song frequency. When the miniature earphone emits brief clicks, mimicking those produced by the natural tymbal mechanism, the model cicada produces sound pulses that vary in duration and shape according to the number and timing of the clicks. A coherent train of two or three resonant clicks results in a long slowly-decaying sound pulse similar to that in the natural song. The natural song frequency can be predicted from the dimensions of the abdominal cavity and the tympana in C. australasiae using a simple equation for the resonant frequency of a Helmholtz resonator. This equation also predicts the song frequency of Macrotristria angularis and Magicicada cassini, but it fails with the low-frequency song of Magicicada septendecim. This discrepancy can be accounted for by the unusually thick tympana of M. septendecim, which tend to lower the resonant frequency of the system. We conclude that the abdomen of male cicadas forms a Helmholtz resonator, the components of which are the large air sac as the cavity and the tympana as the neck of the resonator. We suggest that cicada sound production depends on the coupling of two resonators, that of the tymbal and that of the abdominal air sac, from which sound is radiated through the tympana. The coupled resonator system would produce the long sound pulses required for stimulating a sensitive sharply tuned auditory organ.

One-tone suppression in the cochlear nerve of the gerbil

One-tone rate suppression has been reported several times for auditory nerve fibers of mammalian and non-mammalian vertebrates. Because its properties are very similar to those of two-tone rate suppression, the possibility exists that one-tone rate suppression is the result of an interaction within the inner ear of the suppressing tonal stimulus and some ongoing extraneous acoustic stimulus. For this reason, reports of one-tone rate suppression often elicit suspicions that the investigators were not sufficiently careful in controlling leaks in their acoustic barriers or in the electrical pathways to their acoustic drivers. Recent reports of one-tone rate suppression in pigeon basilar-papillar fibers and goldfish saccular fibers were accompanied by descriptions of measures taken to avoid such leaks. In this paper, we describe one-tone rate suppression in a mammal, the Mongolian gerbil; and we demonstrate that the background spike activity being suppressed is not driven by either external sounds coming from outside the acoustic isolation test chamber or by non-stimulus electrical inputs to the acoustic driver. The suppressed background spike activity evidently arises from sources within the animal. These sources may be non-acoustic, associated with spontaneous pre- or post-synaptic ion-channel activity; or they may be acoustic sources — internal sound or vibration generators.

Cochlear microphonics recorded from fetal and newborn sheep

Purpose: Sounds present within the uterus stimulate the fetal inner ear and central auditory pathway. This study was undertaken to determine the efficiency of transmission of exogenous airborne stimuli to the fetal inner ear. In this way, we may quantify the extent to which the fetal auditory system is isolated from sounds produced outside the mother. Materials and Methods: Cochlear microphonics were recorded from fetal and newborn sheep to evaluate the extent to which the fetus is isolated from sounds exogenous to the ewe. Electrodes were surgically placed in contact with the round window membrane in nine near-term fetal sheep. Cochlear microphonics were recorded in response to 1 3 octave-band noises (0.125 to 2.0 kHz) delivered through a loudspeaker 1.8 m from one side of the pregnant ewe. Sound pressure levels generated by the noises were simultaneously recorded ex utero with a microphone and in utero with a hydrophone previously sutured to the fetal neck. After cochlear microphonic amplitudes were recorded, the fetus was delivered through an abdominal incision. Recordings were repeated from the newborn lamb. Fetal sound isolation was calculated as the difference between the sound pressure levels that were necessary to evoke equal cochlear microphonic amplitudes from the fetus and from the newborn lamb. Results: The sound attenuation observed was variable for all frequencies. The fetus was isolated from external sounds by 11.1 dB for 0.125 kHz, 19.8 dB for 0.25 kHz, 35.3 dB for 0.5 kHz, 38.2 dB for 1.0 kHz, and 45.0 dB for 2.0 kHz. Conclusions: Other investigators have demonstrated that the immature auditory system is more susceptible to damage produced by noise exposure than is the mature auditory system. Low-frequency noise produces damaged cells that later in life code higher frequencies. A possibility of fetal hearing loss produced by intense noise exposure needs more careful evaluation.

Electronic filters, hearing aids and methods

An electronic filter for an electroacoustic system. The system has a microphone for generating an electrical output from external sounds and an electrically driven transducer for emitting sound. Some of the sound emitted by the transducer returns to the microphone means to add a feedback contribution to its electrical output. The electronic filter includes a first circuit for electronic processing of the electrical output of the microphone to produce a first signal. An adaptive filter, interconnected with the first circuit, performs electronic processing of the first signal to produce an adaptive output to the first circuit to substantially offset the feedback contribution in the electrical output of the microphone, and the adaptive filter includes means for adapting only in response to polarities of signals supplied to and from the first circuit. Other electronic filters for hearing aids, public address systems and other electroacoustic systems, as well as such systems and methods of operating them are also disclosed.

Vocalization-correlated single-unit activity in the brain stem of the squirrel monkey

The brain stems of 17 squirrel monkeys (Saimiri sciureus) were systematically explored for vocalization-related single-unit activity during calls electrically elicited from the periaqueductal grey. Of 12,280 cells tested, 1151 fired in relation to vocalization. Of these, 587 reacted to external acoustic stimuli and started firing after vocalization onset. As most of these cells were located in classical auditory relay structures, they probably represent auditory neurones reacting indirectly to self-produced vocalization due to auditory feedback. Seven cells reacted to acoustic stimuli but fired in advance of self-produced vocalization. These cells were located in the pericentral inferior colliculus, dorsal nucleus of the lateral lemniscus, dorsomedial to the ventral nucleus of the lateral lemniscus and immediately lateral to the central grey. They are probably engaged in tuning the auditory system to process self-generated sounds differently from external sounds. 261 neurones reacted to nonphonatory oral movements (chewing, swallowing) and started firing after vocalization onset. These neurones were widely distributed within the brain stem, with the highest density in the spinal trigeminal nucleus and medially adjacent reticular formation. The majority of these cells seem to react to proprioceptive and tactile stimuli generated by phonatory and nonphonatory oral activities. Some of them may exert motor control on muscles that come into play at later stages of phonation. 57 neurones reacted to nonphonatory oral movements but fired in advanced of vocalization onset. These neurones were located mainly in the trigeminal motor nucleus, nucl. ambiguous, reticular formation around these nuclei, parabrachial region and lateral vestibular nucleus. Their role in motor control seems to be related to specific muscles rather than specific functions. 100 of the vocalization-related cells showed a correlation with respiration. Expiration-related cells were found in and around the rostral nucl. ambiguous and in the reticular formation dorsal to the facial nucleus. Inspiration-related cells were located in the rostral and caudal nucl. ambiguous regions, ventrolateral solitary tract nucleus and the lateral reticular formation below the trigeminal motor nucleus. Most of these cells probably represent premotor neurones of respiratory muscles and laryngeal motoneurones of the cricothyroid and posterior cricoarytenoid muscles. Finally, a last group of cells was found that was unresponsive to chewing and swallowing movements, quiet breathing and acoustic stimuli, but changed activity during vocalization. 38 of them became active before vocalization and cricothyroid activity, and 101 afterward.(ABSTRACT TRUNCATED AT 400 WORDS)

Active localization of virtual sounds

A simple virtual sound display built around a microcomputer and analog hardware is described. The display implements most of the primary cues for sound localization in the ear-level plane. Judging both from informal observations by users and from objective data obtained in an experiment on homing to virtual and real sounds, it is concluded that simple displays like the one described are effective in creating the impression of external sounds to which observers can locomote with ease; in particular, this means that simulation of the direction-dependent spectral shaping effects of the pinnae is not a necessary requirement for extracranial sound localization.

Sound environment of the fetal sheep

The internal sound pressure levels within the intact amnion of pregnant ewes surgically implanted with a hydrophone was determined during conditions of quiet and during sound field exposures to broadband and octave-band noise. Measurements were made of sound pressures outside and inside the ewe, and sound attenuation through maternal tissues and fluids was calculated. Sound pressures generated by low frequencies (less than 0.25 kHz) were 2 to 5 dB greater inside than outside the ewe. Above 0.25 kHz, sound attenuation increased at a rate of 6 dB per octave. For 4.0 kHz, sound attenuation averaged 20 dB. The sound pressure recorded at different locations within the amnion with respect to the sound source varied by up to 6 dB. The internal noise floor in the absence of externally generated sounds was as low as 50 dB (spectrum level) above 0.2 kHz. Thus the fetus is developing in an environment that is rich with internal and external sounds.

Predictors of tinnitus discomfort, adaptation and subjective loudness

In a nation-wide investigation, covering all the hearing centres in Sweden, a study was made of adaptation processes, subjective discomfort from tinnitus, subjective loudness of tinnitus and psychological complaints in 3372 subjects by means of a questionnaire. The most important predictors of discomfort from and adaptation to tinnitus were found to be the controllability and the degree of maskability by external sounds, i.e. the subject's coping abilities or internal-external locus of control. Increased control and masking effects from the environment imply a decrease in discomfort and better adaptation. The most important predictor of worsened subjective loudness of tinnitus was the duration of the tinnitus. That is, subjects who had had tinnitus for a longer time perceived the loudness as more intense. The psychosomatic factors which most strongly predicted increased discomfort from and decreased tolerance to tinnitus were depression and insomnia. These findings have theoretical and practical implications for the management and treatment of tinnitus.

揺らぎの確率情報に整合した外来雑音下のシステム同定と遮音システム

As is well-known, most of conventional studies on the sound insulation system were introduced mainly from the deterministic viewpoint in a frequency domain or based on the linear correlation technique in a time domain. However, in the actual noise environment, the resultant signal often shows a complicated fluctuation pattern apart from the usual Gaussian type, owing to the variety of phenomena and the complexity of human response, and the actual observation is inevitably contaminated very often by a background noise of arbitrary distribution type. Therefore, in this paper, an identification method of arbitrary sound insulation systems contaminated by a background noise is proposed, under the evaluation criterion based on the agreement between theory and experiment for the output probability distribution, especially by paying our attention to not only the lower order statistical information like mean and variance but also the higher order statistical one which is directly matched to the actual noise evaluation idices Lx (X=95, 90, 10, 5). Concretely, these systems are first described in a non-linear equation on the power flow in a time domain. Then, by newly introducing an error criterion on the deviation from the actually observed output probability distribution, a recurrence estimation algorithm for system parameter is introduced from three different viewpoints by use of the well-known stochastic approximation method. Finally, the effectiveness of our proposed method is confirmed experimentally by applying it to the non-parallel type double wall and sound-bridge type shielding systems which are very difficult to evaluate by the already-known theoretical analyses.

OBJECTIVE ASSESSMENT OF ACUTE VIRAL CROUP

There is little evidence that any medication is helpful in acute viral croup but few studies have attempted objective measurement of the stridor before and after treatment. We have devised a small microphone which can be easily attached to the child's neck by double sided adhesive tape. The microphone predominantly responds to vibration and is unresponsive to external sounds. Tape recordings were made before and 15 minutes after nebulised therapy. The response to nebulised adrenaline, ipratropium bromide, xylometazoline clemastine and placebo were observed in a double blind manner. Inspiratory and expiratory components were separated by listening to the tape whilst concurrently viewing the output on a BBC microcomputer vide display unit (VDU). The measurement was expressed by integrating the sound amplitude over the period of inspiratory noise. There was little response to any medication in children under 2 years of age but the response increased with age. Improvement in the microphone trace correlated well with clinical improvement. Conclusion - We present evidence to show that medications (especially adrenaline) can be helpful in acute viral croup in children over 2 years of age.