Sound attenuation for low frequencies, in particular for air ducts in paper mills

1994 ◽  
Vol 96 (3) ◽  
pp. 1946-1946
Author(s):  
H. Pettersson
Keyword(s):  
Sound Attenuation ◽  
Low Frequencies ◽  
Paper Mills

An Analysis of Deep Ocean Sound Attenuation at Very Low Frequencies

1982 ◽  
Author(s):  
Karl C. Focke ◽  
Stephen K. Mitchell ◽  
Sr Horton ◽  
Claude W.
Keyword(s):  
Deep Ocean ◽  
Sound Attenuation ◽  
Low Frequencies

scholarly journals Sound attenuation by conglomerates of bubbles at low frequencies

1976 ◽  
Vol 60 (S1) ◽  
pp. S35-S35
Author(s):  
K. J. Diercks ◽  
W. B. Huckabay
Keyword(s):  
Sound Attenuation ◽  
Low Frequencies

Analysis of deep ocean sound attenuation at very low frequencies

1982 ◽  
Vol 71 (6) ◽  
pp. 1438-1444 ◽  
Author(s):  
Karl C. Focke ◽  
S. K. Mitchell ◽  
C. W. Horton
Keyword(s):  
Deep Ocean ◽  
Sound Attenuation ◽  
Low Frequencies

scholarly journals The Sound of Tropical Cyclones

2014 ◽  
Vol 44 (10) ◽  
pp. 2763-2778 ◽  
Author(s):  
Zhongxiang Zhao ◽  
Eric A. D’Asaro ◽  
Jeffrey A. Nystuen
Keyword(s):  
Wind Speed ◽  
Tropical Cyclones ◽  
Wind Waves ◽  
Sound Field ◽  
Sound Level ◽  
Sound Attenuation ◽  
Low Frequencies ◽  
Wind Speeds ◽  
Sound Levels ◽  
Breaking Wind Waves

Abstract Underwater ambient sound levels beneath tropical cyclones were measured using hydrophones onboard Lagrangian floats, which were air deployed in the paths of Hurricane Gustav (2008) and Typhoons Megi (2010) and Fanapi (2010). The sound levels at 40 Hz–50 kHz from 1- to 50-m depth were measured at wind speeds up to 45 m s−1. The measurements reveal a complex dependence of the sound level on wind speed due to the competing effects of sound generation by breaking wind waves and sound attenuation by quiescent bubbles. Sound level increases monotonically with increasing wind speed only for low frequencies (<200 Hz). At higher frequencies (>200 Hz), sound level first increases and then decreases with increasing wind speed. There is a wind speed that produces a maximum sound level for each frequency; the wind speed of the maximum sound level decreases with frequency. Sound level at >20 kHz mostly decreases with wind speed over the wind range 15–45 m s−1. The sound field is nearly uniform with depth in the upper 50 m with nearly all sound attenuation limited to the upper 2 m at all measured frequencies. A simple model of bubble trajectories based on the measured float trajectories finds that resonant bubbles at the high-frequency end of the observations (25 kHz) could easily be advected deeper than 2 m during tropical cyclones. Thus, bubble rise velocity alone cannot explain the lack of sound attenuation at these depths.

Transmission of Airborne Sound from 50-20,000 Hz into the Abdomen of Sheep

1993 ◽  
Vol 12 (1) ◽  
pp. 16-24 ◽  
Author(s):  
Aemil J.M. Peters ◽  
Robert M. Abrams ◽  
Kenneth J. Gerhardt ◽  
Scott K. Griffiths
Keyword(s):  
Pregnant Woman ◽  
Occupational Health ◽  
Health Professionals ◽  
Sound Pressure ◽  
Stimulus Level ◽  
Pressure Level ◽  
Sound Attenuation ◽  
Frequency Range ◽  
Low Frequencies ◽  
High Frequencies

The transmission of audible sounds from the environment of the pregnant woman to the foetus is of growing interest to obstetricians who utilize foetal vibracoustic stimulation in their examinations, and to occupational health professionals who believe that high-intensity sound in the workplace is potentially damaging to the foetus. Earlier reports on transmission of sound into the abdomen and uterus of sheep revealed a significant amount of sound attenuation at frequencies above 2,000 Hz. and some enhancement at frequencies below 250 Hz. However, frequencies above 10,000 Hz, and stimulus levels as possible variables, were not studied. In this report, the effects of frequency from 50-20,000 Hz. and stimulus levels (90 to 110 dB sound pressure level), were studied in five sheep. Sound attenuation varied as a function of frequency (p<0.001). Sound attenuation varied inversely as a function of stimulus level for low frequencies (50-125 Hz) and for high frequencies (7,000–20,000 Hz) (p<0.001). In the mid frequency range (200-4,000 Hz), no effect of stimulus level (p=0.96) was found. Additionally, in the 800-2,000 Hz range there was enhancement of sound pressure of up to 10 dB.

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