scholarly journals Hearing in the African lungfish ( Protopterus annectens ): pre-adaptation to pressure hearing in tetrapods?

2010 ◽  
Vol 7 (1) ◽  
pp. 139-141 ◽  
Author(s):  
Jakob Christensen-Dalsgaard ◽  
Christian Brandt ◽  
Maria Wilson ◽  
Magnus Wahlberg ◽  
Peter T. Madsen
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
West African ◽  
Low Frequencies ◽  
Frequency Responses ◽  
Protopterus Annectens ◽  
Vibration Detection ◽  
Low Frequency Vibration ◽  
African Lungfish ◽  
Early Tetrapods

Lungfishes are the closest living relatives of the tetrapods, and the ear of recent lungfishes resembles the tetrapod ear more than the ear of ray-finned fishes and is therefore of interest for understanding the evolution of hearing in the early tetrapods. The water-to-land transition resulted in major changes in the tetrapod ear associated with the detection of air-borne sound pressure, as evidenced by the late and independent origins of tympanic ears in all of the major tetrapod groups. To investigate lungfish pressure and vibration detection, we measured the sensitivity and frequency responses of five West African lungfish ( Protopterus annectens ) using brainstem potentials evoked by calibrated sound and vibration stimuli in air and water. We find that the lungfish ear has good low-frequency vibration sensitivity, like recent amphibians, but poor sensitivity to air-borne sound. The skull shows measurable vibrations above 100 Hz when stimulated by air-borne sound, but the ear is apparently insensitive at these frequencies, suggesting that the lungfish ear is neither adapted nor pre-adapted for aerial hearing. Thus, if the lungfish ear is a model of the ear of early tetrapods, their auditory sensitivity was limited to very low frequencies on land, mostly mediated by substrate-borne vibrations.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

The Sound Environment of the Foetal Sheep

Behaviour ◽  
1982 ◽  
Vol 81 (2-4) ◽  
pp. 296-315 ◽  
Author(s):  
B.A. Baldwin ◽  
B.C.J. Moore ◽  
Sally E. Armitage ◽  
J. Toner ◽  
Margaret A. Vince
Keyword(s):  
Sound Pressure ◽  
Body Wall ◽  
Low Frequency ◽  
Sound Level ◽  
The Body ◽  
Human Foetus ◽  
Low Frequencies ◽  
Sound Environment ◽  
High Sound ◽  
Foetal Lamb

AbstractThe sound environment of the foetal lamb was recorded using a hydrophone implanted a few weeks before term in a small number of pregnant ewes. It was implanted inside the amniotic sac and sutured loosely to the foetal neck, to move with the foetus. Results differ from those reported earlier for the human foetus: sounds from the maternal cardiovascular system were picked up only rarely, at very low frequencies and at sound pressures around, or below, the human auditory threshold. Other sounds from within the mother occurred intermittently and rose to a high sound pressure only at frequencies above about 300 Hz. Sounds from outside the mother were picked up by the implanted hydrophone when the external sound level rose above 65-70 dB SPL, and the attenuation in sound pressure was rarely more than 30 dB and, especially at low frequencies, usually much less. However, attenuation due to the transmission of sound through the body wall and other tissues tended to change from time to time. It is concluded that the foetal lamb's sound environment consists of (1) intermittent low frequency sounds associated largely with the ewe's feeding and digestive processes and (2) sounds such as vocalisations from the flock, human voices and other sounds from outside the mother.

Low Frequency Vibration Detection and Compensation in Hard Disk Drive

2011 ◽  
Vol 47 (7) ◽  
pp. 1964-1969 ◽  
Author(s):  
Wen-Jun Cao ◽  
JianYi Wang ◽  
MingZhong Ding ◽  
Qiang Bi ◽  
KianKeong Ooi
Keyword(s):  
Hard Disk Drive ◽  
Low Frequency ◽  
Hard Disk ◽  
Disk Drive ◽  
Vibration Detection ◽  
Low Frequency Vibration

Reduction of the Sound Pressure Radiated by a Submarine by Isolation of the End Caps

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Mauro Caresta ◽  
Nicole J. Kessissoglou
Keyword(s):  
Sound Pressure ◽  
Low Frequency ◽  
Axial Direction ◽  
Radial Component ◽  
Axial Motion ◽  
Low Frequencies ◽  
End Caps ◽  
Passive Isolation ◽  
Radiated Sound ◽  
Finite Cylindrical Shell

A passive isolation approach to reduce the sound pressure radiated by a submarine is presented. The submerged vessel is modeled as a stiffened cylindrical hull partitioned by bulkheads and with two end caps of conical shape. Fluctuating forces from the propeller are transmitted to the hull through the shaft and a rigid foundation, resulting in axisymmetric excitation of the hull. The hull surface motion is mainly in the axial direction with a small radial component due to the coupling between the two orthogonal shell displacements. The sound pressure resulting from the axial motion is radiated from the end caps of the submarine. This work investigates reduction of the far field sound pressure by passive isolation of the end caps from the main hull. Isolation of the axial motion of the end caps from the cylindrical hull results in significant reduction of the radiated sound at low frequencies. The fluid loading approximation for a finite cylindrical shell in the low frequency range is also discussed.

A MEMS resonant accelerometer for low-frequency vibration detection

2018 ◽  
Vol 283 ◽  
pp. 151-158 ◽  
Author(s):  
Shudong Wang ◽  
Xueyong Wei ◽  
Yulong Zhao ◽  
Zhuangde Jiang ◽  
Yajing Shen
Keyword(s):  
Low Frequency ◽  
Vibration Detection ◽  
Low Frequency Vibration ◽  
Resonant Accelerometer

Low Frequency Calibration of Measurement Microphones

2009 ◽  
Vol 28 (3) ◽  
pp. 223-228 ◽  
Author(s):  
Gunnar Rasmussen ◽  
Kim M. Nielson
Keyword(s):  
Frequency Response ◽  
Sound Pressure ◽  
Low Frequency ◽  
Constant Force ◽  
Low Frequencies ◽  
Proportional Relation ◽  
Frequency Calibration ◽  
Large Piston

The calibration of measurement microphones below 100 Hz is not very well covered by the present IEC standards. The uncertainty increases rapidly and for very low frequencies it goes toward infinity. This paper approaches this issue and presents a unique way to verifying and calibrating the low-frequency response of measurement microphones. Using a small isolated calibration volume and applying a constant force to a large piston inside this volume, you obtain a direct proportional relation between force and sound pressure, allowing calibration of measurement microphones down to 0.01 Hz.

Probe-Tube Microphone Measures of Vent Effects With In-the-Canal Hearing Aid Shells

1992 ◽  
Vol 1 (2) ◽  
pp. 58-62 ◽  
Author(s):  
Andrew Stuart ◽  
Robert Stenstrom ◽  
Odilia MacDonald ◽  
Mark P. Schmidt ◽  
Gail MacLean
Keyword(s):  
Sound Pressure Level ◽  
Sound Pressure ◽  
Hearing Aid ◽  
Low Frequency ◽  
Pressure Level ◽  
Frequency Responses ◽  
Upward Shift

The acoustic effects of three different configurations of vented in-the-canal (ITC) hearing aid shells were investigated. Real-ear sound pressure level measures (200–2000 Hz) were obtained from unvented and vented ITC shells from 12 adult subjects. In general, with increasing vent size, an increase in the amount of low-frequency reduction and an upward shift in vent kneepoints and vent-associated resonance occurred. The use of venting may be considered clinically for low-frequency reduction in ITC hearing aid frequency responses.

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