Sound Pressure Difference Research Articles

Verifying the attenuation of earplugs in situ: variability of transfer functions among human subjects

The use of in situ measurements of hearing protectors' (HPD's) attenuation following the MIRE‐protocol (Microphone In Real Ear) is increasing. The attenuation is hereby calculated from the difference in sound levels outside the ear and inside the ear canal behind the HPD. Custom‐made earplugs have been designed with an inner bore that allows inserting a miniature microphone. A thorough understanding of the difference, henceforth called 'transfer function', between the sound pressure of interest at the eardrum and the one measured at the inner bore of the HPD is indispensable for optimizing this technique and extending its field of application. Of particular interest is the variation of these transfer functions among humans. This was checked experimentally on 19 subjects. Differences in sound pressure were measured at the HPD's inner bore, by the MIRE‐microphone, and at the eardrum by inserting an extra tube microphone in the ear canal. All transfer functions showed a comparable shape, however variability was substantial for the exact frequency and amplitude of the resonance peaks. The link between this variability and the morphology of the individual's HPD and ear canal was addressed using FDTD‐simulations (Finite‐Difference Time‐Domain) of the outer ear canal occluded by an earplug with inner bore.

Non-ossicular signal transmission in human middle ears: Experimental assessment of the “acoustic route” with perforated tympanic membranes

Direct acoustic stimulation of the cochlea by the sound-pressure difference between the oval and round windows (called the "acoustic route") has been thought to contribute to hearing in some pathological conditions, along with the normally dominant "ossicular route." To determine the efficacy of this acoustic route and its constituent mechanisms in human ears, sound pressures were measured at three locations in cadaveric temporal bones [with intact and perforated tympanic membranes (TMs)]: (1) in the external ear canal lateral to the TM, P(TM); (2) in the tympanic cavity lateral to the oval window, P(OW); and (3) near the round window, P(RW). Sound transmission via the acoustic route is described by two concatenated processes: (1) coupling of sound pressure from ear canal to middle-ear cavity, H(P(CAV) ) identical withP(CAV)P(TM), where P(CAV) represents the middle-ear cavity pressure, and (2) sound-pressure difference between the windows, H(WPD) identical with(P(OW)-P(RW))P(CAV). Results show that: H(P(CAV) ) depends on perforation size but not perforation location; H(WPD) depends on neither perforation size nor location. The results (1) provide a description of the window pressures based on measurements, (2) refute the common otological view that TM perforation location affects the "relative phase of the pressures at the oval and round windows," and (3) show with an intact ossicular chain that acoustic-route transmission is substantially below ossicular-route transmission except for low frequencies with large perforations. Thus, hearing loss from TM perforations results primarily from reduction in sound coupling via the ossicular route. Some features of the frequency dependence of H(P(CAV) ) and H(WPD) can be interpreted in terms of a structure-based lumped-element acoustic model of the perforation and middle-ear cavities.

Objective assessment of autophony in patients with patulous Eustachian tube

The objective of the present study is to evaluate the Eustachian tube (ET) acoustic patency during phonation. The sound level in the EAC during phonation of the "A" and "N" sounds was measured by microphones in the bilateral EACs of nine normal subjects and 31 patients with patulous ET. The measured sound pressure differences between the right and left ears were correlated with the differences in severity of autophony between the bilateral ears assessed by a visual analogue scale (VAS). The patulous condition was often remarkable when the "N" sound was phonated. In some patients with patulous ET, the patulous condition was indicated only by the present method, and not by conventional ET function tests such as tubo-tympano-aerodynamic-graphy or sonotubometry.

1A1-M06 スピーカの出力変化による120ch平面スピーカアレイの、1焦点、2焦点形成時のサイドローブ減少(人間機械協調)

This paper aims decreasing side lobes and gets high sound pressure difference between sound spot and other points. The side lobe is small and the output of the speaker for the width of the main lobe to come not to exceed 45cm was requested from the silulation, and it measured it. The measurement result showed to control the existing high pitched sound pressure areas of about 5dB other than the focus in a past DSBF method.

2P1-E22 スピーカの出力変化による平面スピーカアレイの焦点での高音圧化とサイドローブ減少

This paper aims decreasing side lobes and gets high sound pressure difference between sound spot and other points. In order to side lobes, we propse two way. One is "number of speaker interval of speaker/wavlength "enlarged. Other is speaker output control. After authores confirm effect by using each poposal technique by simulation, we measure by using 256ch plane speaker array. The measurement result showed to control the existing high pitched sound pressure areas of 70〜75dB other than the focus in a past DSBF method.

How Does the Sound Pressure Generated by Circumaural, Supra-aural, and Insert Earphones Differ for Adult and Infant Ears?

To determine how the ear canal sound pressure levels generated by circumaural, supra-aural, and insert earphones differ when coupled to the normal adult and infant ear. The ratio between the sound pressure generated in an adult ear and an infant ear was calculated for three types of earphones: a circumaural earphone (Natus Medical, ALGO with Flexicoupler), a supra-aural earphone (Telephonics, TDH-49 with MXAR cushion), and an insert earphone placed in the ear canal (Etymoup and down arrow tic Research, ER-3A). The calculations are based on (1) previously published measurements of ear canal impedances in adult and infant (ages 1, 3, 6, 12, and 24 months) ears (Keefe et al., 1993, Acoustic Society of America, 94:2617-2638), (2) measurements of the Thévenin equivalent for each earphone configuration, and (3) acoustic models of the ear canal and external ear. Sound-pressure levels depend on the ear canal location at which they are measured. For pressures at the earphone: (1) Circumaural and supra-aural earphones produce changes between infant and adult ears that are less than 3 dB at all frequencies, and (2) insert earphones produce infant pressures that are up to 15 dB greater than adult pressures. For pressures at the tympanic membrane: (1) Circumaural and supra-aural earphones produce infant pressures that are within 2 dB of adult ears at frequencies below 2000 Hz and that are 5 to 7 dB smaller in infant ears than adult ears above 2000 Hz, and (2) insert earphones produce pressures that are 5 to 8 dB larger in infant ears than adult ears across all audiometric frequencies. Sound pressures generated by all earphone types (circumaural, supra-aural, and insert) depend on the dimensions of the ear canal and on the impedance of the ear at the tympanic membrane (e.g., infant versus adult). Specific conclusions depend on the location along the ear canal at which the changes between adult and infant ears are referenced (i.e., the earphone output location or the tympanic membrane). With circumaural and supra-aural earphones, the relatively large volume of air within the cuff of the earphone dominates the acoustic load that these earphones must drive, and differences in sound pressure generated in infant and adult ears are generally smaller than those with the insert earphone in which the changes in ear canal dimensions and impedance at the tympanic membrane have a bigger effect on the load the earphone must drive.

Stimulus-frequency otoacoustic emissions measured with amplitude-modulated suppressor tones

Stimulus-frequency otoacoustic emissions (SFOAEs) are typically derived as the difference in sound pressure in the ear canal with and without a suppressor tone added to the probe tone. A novel variation of this method applies a sinusoidal amplitude modulation (AM) to the suppressor tone, which causes the SFOAE to also be modulated. The AM-SFOAE can be separated from the probe frequency using spectral methods. AM-SFOAE measurements are described for four normal-hearing subjects using 6-Hz AM. Because the suppressor modulation is at a higher rate, the AM-SFOAE technique avoids the confounding influence of heartbeat, which also modulates the probe tone.

Marine mammals and noise: Problems with root mean square sound pressure levels for transients

Current mitigation levels for noise transients impinging on marine mammals are specified by rms pressures. The rms measure critically relies upon choosing the size of averaging window for the squared pressures. Derivation of this window is not standardized, which can lead to 2-12 dB differences in rms sound pressure for the same wave forms. rms pressure does not represent the energy of the noise pulse and it does not prevent exposure to high peak pressures. Safety levels for transients should therefore be given by received peak-peak sound pressure and energy flux density instead of rms sound pressure levels.

SO MANY INSECTS, SO MANY SIGNALS

Edited by P. D. Evans London: Academic Press (2002) 428p. ISBN 012024229X £89.95 hardback. ![Figure][1] Reviews published in Advances in Insect Physiology are typically comprehensive treatments of an area by renowned experts in the field, and volume 29 is no

How do Tympanic-membrane Perforations Affect Human Middle-ear Sound Transmission?

Although tympanic-membrane (TM) perforations are common sequelae of middle-ear disease, the hearing losses they cause have not been accurately determined, largely because additional pathological conditions occur in these ears. Our measurements of acoustic transmission before and after making controlled perforations in cadaver ears show that perforations cause frequency-dependent loss that: (1) is largest at low frequencies; (2) increases as perforation size increases; and (3) does not depend on perforation location. The dominant loss mechanism is the reduction in sound-pressure difference across the TM. Measurements of middle-ear air-space sound pressures show that transmission via direct acoustic stimulation of the oval and round windows is generally negligible. A quantitative model predicts the influence of middle-ear air-space volume on loss; with larger volumes, loss is smaller.

Isolating the auditory system from acoustic noise during functional magnetic resonance imaging: examination of noise conduction through the ear canal, head, and body.

Approaches were examined for reducing acoustic noise levels heard by subjects during functional magnetic resonance imaging (fMRI), a technique for localizing brain activation in humans. Specifically, it was examined whether a device for isolating the head and ear canal from sound (a "helmet") could add to the isolation provided by conventional hearing protection devices (i.e., earmuffs and earplugs). Both subjective attenuation (the difference in hearing threshold with versus without isolation devices in place) and objective attenuation (difference in ear-canal sound pressure) were measured. In the frequency range of the most intense fMRI noise (1-1.4 kHz), a helmet, earmuffs, and earplugs used together attenuated perceived sound by 55-63 dB, whereas the attenuation provided by the conventional devices alone was substantially less: 30-37 dB for earmuffs, 25-28 dB for earplugs, and 39-41 dB for earmuffs and earplugs used together. The data enabled the clarification of the relative importance of ear canal, head, and body conduction routes to the cochlea under different conditions: At low frequencies (< or =500 Hz), the ear canal was the dominant route of sound conduction to the cochlea for all of the device combinations considered. At higher frequencies (>500 Hz), the ear canal was the dominant route when either earmuffs or earplugs were worn. However, the dominant route of sound conduction was through the head when both earmuffs and earplugs were worn, through both ear canal and body when a helmet and earmuffs were worn, and through the body when a helmet, earmuffs, and earplugs were worn. It is estimated that a helmet, earmuffs, and earplugs together will reduce the most intense fMRI noise levels experienced by a subject to 60-65 dB SPL. Even greater reductions in noise should be achievable by isolating the body from the surrounding noise field.

Acoustic mechanisms: Canal wall-up versus canal wall-down mastoidectomy

The contribution of the middle ear air spaces to sound transmission through the middle ear in canal wall-up and canal wall-down mastoidectomy was studied in human temporal bones by measurements of middle ear input impedance and sound pressure difference across the tympanic membrane for the frequency range 50 Hz to 5 kHz. These measurements indicate that, relative to canal wall-up procedures, canal wall-down mastoidectomy results in a 1 to 5 dB decrease in middle ear sound transmission below 1 kHz, a 0 to 10 dB increase between 1 and 3 kHz, and no change above 3 kHz. These results are consistent with those reported by Gyo et al. (Arch Otolaryngol Head Neck Surg 1986;112:1262-8), in which umbo displacement was used as a measure of sound transmission. A model analysis suggests that the reduction in sound transmission below 1 kHz can be explained by the smaller middle ear air space volume associated with the canal wall-down procedure. We conclude that as long as the middle ear air space is aerated and has a volume greater than 0.7 ml, canal wall-down mastoidectomy should generally cause less than 10 dB changes in middle ear sound transmission relative to the canal wall-up procedure. (Otolaryngol Head Neck Surg 1998;118:751-61.)

Sound pressure transformation at the pinna of Mus domesticus.

Sound pressure transformation properties at the pinna of laboratory mice Mus domesticus were studied by measuring the sound pressure level of a continuous tone at a series of frequencies at the tympanic membrane as a function of the position of a sound source under free-field stimulation conditions. The spectral transformation, the interaural spectral difference, the isopressure contours and the interaural pressure difference contours were plotted. Sound pressure transformation functions showed some prominent spectral notches throughout the frequency range tested (10-80 kHz). However, the notch frequency did not appear to be systematically related to sound direction. The study of interaural pressure difference demonstrated that, when delivered from some angles within the ipsilateral frontal hemisphere, the sound pressure at the tympanic membrane of certain frequencies may be lower than that determined at the corresponding contralateral angles. For each sound frequency tested, there was an angle (the acoustic axis) within the ipsilateral frontal hemisphere from which the delivered sound reached a maximal pressure level at the tympanic membrane. However, the acoustic axis often changed to a new angle after removal of the ipsilateral pinna. In addition, sound delivered from the acoustic axis did not always generate a maximal pressure transformation. The isopressure contours determined within 2-5 dB of the maximal pressure were circumscribed, and their contained angular areas were found to decrease with increasing sound frequency. The 2 dB maximal pressure area may appear at more than one angular area for some test frequencies. Removal of the ipsilateral pinna or modification of pinna posture expanded isopressure contours irregularly and split the 2 dB maximal pressure area into several parts. The sound pressure difference determined between the angles of maximal and minimal sound pressure (the maximal directionality) increased with sound frequency regardless of pinna posture. Acoustic gain of the pinna at the acoustic axis reached 6-12 dB, depending upon sound frequency. However, the pinna gain was not always maximal at the acoustic axis for a given frequency.

Sensitivity to varying gains and losses: The role of self- discrepancies and event framing.

Three studies psychophysically measured people's discrimination among different sizes of monetary net gains or net losses. Participants imagined either gains or nonlosses (i.e., net gains) or losses or nongains (i.e., net losses). Participants discriminated more when the identical event was framed as the presence (gains and losses) versus the absence (nonlosses and nongains) of an outcome, presumably because the latter is harder to represent. Discrimination was enhanced when the motivational features of the imagined event were either both the same as or both different from a person's selfdiscrepancy. Discrimination was reduced when only one of the motivational features was different. A model of excitations, inhibitions, and disinhibitions between mental representation is suggested to account for these findings. When people perceive an increase in the loudness of a tone as a result of an increase in its sound pressure, their sensory discriminates between these two physical sound pressures. They experience this increase in stimulus intensity as an increase in loudness. A highly discriminating sensory system tracks the slightest variation of stimulus intensity. It is sensitive to differences in stimulus intensity, such as sound pressure differences. In contrast, a nondiscriminat ing system does not detect variations in stimulus intensity, even when they are fairly large. Such a system is insensitive to differences in stimulus intensity. Different sensory systems can have different discriminations or one system can have different discriminations as a function of specific variables. Positive and negative events can also have different stimulus intensities. For example, when people perceive a difference in the of two monetary losses, such as the difference between a $50 loss and a $60 loss, their affective apparatus discriminates between two stimulus intensities (here money

Studies on the generation mechanism of non-biological response in distortion product OTO-acoustic emission

We investigated the effect of non-biological artifacts on the measurement of distortion product oto-acoustic emission (DPOAE) using guinea pigs, and the generation mechanism of this phenomenon is discussed in the present paper. When a sound pressure of a stimulating tone was too large, an overtone was produced within the acoustic probe. When the difference in sound pressure between f1 and f2 was too large, artifacts appeared at frequencies of 2f1-f2 or 2f2-f1. Similar responses were generated when f1 and f2 were identical in sound pressure but exceeded a certain critical level. These non-biological responses could be easily differentiated from biological responses by subjecting the animal to anoxia. The input-output curve of DPOAE was biphasic and clearly showed this critical level in each animal. The results obtained in the present study suggest that the levels of f1 and f2 should be almost equal and should not exceed the observed critical level when measuring DPOAE.

騒音環境下での音源選択法

A new algorithm for signal processing to improve the hearing ability of hearing aid users under noisy circumstances is proposed.In the auditory system, the sound directions are detected precisely by analyzing two kinds of information; 1) the interaural time difference and 2) the interaural sound pressure difference. Using a personal computer, acoustic signals were analyzed according to an algorithm similar to that of the auditory system. The sound coming from the optional direction could be readily detected. If this algorithm is applied to the electric circuits of hearing aids, the user's hearing ability under noisy circumstances could be improved greatly.

Tympanometry using a sweep-frequency probe tone and its clinical evaluation.

In this new tympanometric system, air pressure in the external meatus is kept constant at either -200 daPa or 0 daPa. The frequency of the probe tone is swept from 220 to 2,000 Hz (or 2,500 Hz, if necessary) in 4 s. During this frequency sweep, sound pressure in decibels and phase angle in degrees in the external meatus are sampled and the differences in sound pressure and phase angle measured at -200 and 0 daPa pressures are computed. These results are figured as a frequency-sound pressure curve and a frequency-phase angle curve. From the study on 8 fresh human cadaver temporal bones, four parameters in these curves are selected by discriminant analysis to provide diagnostic criteria: the minimum value and the 0-cross frequency of the frequency-sound pressure curve and the maximum value and its frequency of the frequency-phase angle curve. Normal parameters were determined in 50 normal ears. Evaluation of 40 patients with ossicular disorders revealed that 10 out of 12 cases of ossicular discontinuity and 5 out of 6 cases of malleus and/or incus fixation were correctly diagnosed. For stapes fixation, the diagnosis was correct in 12 out of 22 ears. This system is useful in the clinical diagnosis of ossicular disorders, producing a collection of curves and parameters that are distinctively different for the ossicular discontinuity and the ossicular fixation.

Acoustic intensity techniques for airplane cabin applications

A technique to measure surface radiation from an airplane cabin in flight using a two-microphone acoustic intensity system is described. The technique addresses the problems of high background levels and surface absorption that have in the past complicated cabin radiation measurements. Two probe types were used: a bare probe for the reflective sidewall and ceiling regions and a shielded probe for the absorptive carpet. Laboratory tests were conducted to establish the accuracy and tolerance to background noise for the flight measurement system. From these tests the operating range for each probe was determined in terms of the difference in sound pressure and intensity levels. This difference, called the signal-to-noise indicator, was used to screen out flight data saturated by the background field. From the cabin surveys, several strong radiation areas, such as the ceiling panel and the air distribution and air return grills, were measured quantitatively. Small area sources were distinguished from adjacent areas, and other weak sources were identified.

Studies for diagnostic method for ossicular lesions

The diagnosis of the ossicular condition, fixation or interruption, is often not achieved by the routine tympanometry. A new tympanometric system has been developed in order to improve the diagnostic value. This produces a sweep-frequency probe tone of 200 to 2000Hz and measures the sound pressure difference and the phase difference between the output and the input.An experimental study was performed using eight fresh human temporal bones. Sound pressure curves and phase angle curves were figurized against the probe tone frequency in three conditions of the ossicular chain: normal, fixation glued by dental cement, and interruption made by mechanical separation. In addition, static compliance was also obtained by the conventional tympanometry. A multivariate analysis was performed to obtain the effective variables which would be a good indicator for the change in transmission characteristics of the ossicular chain. The results showed static compliance was less valuable than other variables of the sound pressure curve and the phase angle curve. Among these variables, four were selected as the most valuable ones from the result of a discriminant analysis.These four variables were clinically applied to differentiate three groups of the ossicular pathology: staps fixation, malleus or incus fixation and incudostapedial disconnection. The internal and external check using the discriminant function were performed in forty ears, in which ossicular lesions were surgically confirmed. This resulted in a high ratio of differentiation. Thus, this system can be of great value in the diagnosis of ossicular abnormalities.

Sound Pressure at the Entrance of the External Meatus as a Function of the Azimuth of a Tone

Sound pressure of tones of 4, 10, and 20 kHz was measured at the external meatus as a function of the azimuth of the source. The measurements were made under free-field conditions in man, squirrel monkey, bat, and rat. At 4 kHz, rat and man showed consistent variations of sound pressure as a function of azimuth. Interaural intensity differences were estimated to be sufficient to support localization of a tone at a minimum angle of 2.1° (rat) and 1.13° (man) from the midline. No regular sound pressure differences were obtained in bat and squirrel monkey. At 10 and 20 kHz, rat, bat, and monkey showed consistent variations of sound-pressure level with azimuth of at least 15 dB. Interaural differences were sufficient to support localization of a 10-kHz tone at 1.13° (monkey), 2.0° (bat), and 1.5° (rat). Similar results were obtained at 20 kHz. No measurements were made on man at 10 and 20 kHz. [Supported by the National Science Foundation.]