Measurement of low-frequency underwater noise by a self-recording hydrophone

Bong-Chae Kim, Hongsang Cho, Byoung-Nam Kim,Chang-Woong Shin, Donggoog Kim, and Bok Kyung Choi

Marine Environment Research DepartmentKorea Ocean Research & Development Institute

Objectives of this study

To test a newly developed self-recording hydrophone to measure low-frequency underwater noise in the sea

To acquire low-frequency ocean noise data at a site in the South Sea of Korea

To investigate correlation between noise levels and environment variables

Block diagram and specifications ofself-recording hydrophone

Receiving frequency characteristics ofself-recording hydrophone

Self-recording hydrophone

B&K 8103 hydrophone

SD memory

Battery

Measurement site

KOREA

JAPAN

CHINA

Yellow Sea

East Sea

Korea Strait●

siteSouth Sea

Instruments installation for noise measurement

Hydrophone(20 m)

10 m10 m

10 mR/V Eardo

Sea bed

52 m Hydrophone(40 m)

ADCP

5 m

RadarAnemometer

Self-recording hydrophone

Sea surface

CTD

Recording and spectrum analysis systemby conventional cabled hydrophone

Instrumentation cassette recorder

(Sony PC208Ax)

Oscilloscope

(LeCroy LT264M)

Measuring amplifier

(B&K 2636)

Hydrophone

(B& K 8106)

Recording

Personal computer

A/D converter

(NI PCI-6034E, 16bit)

Spectrum analysis

(DADiSP 2002)

Spectrum analysis

Instrumentation cassette recorder

(Sony PC208Ax)

Environment variables

Averaged noise spectrum level

Mean and standard deviation ofnoise spectrum level

Correlation between wind speed and noise level (20 m depth)

Correlation coefficient = 0.0323 Correlation coefficient = -0.1266

Correlation between wind speed and noise level (40 m depth)

Correlation coefficient = 0.0286 Correlation coefficient = -0.2638

Correlation between wind speed and noise level (52 m depth)

Correlation coefficient = 0.1435 Correlation coefficient = 0.0037

Correlation between current velocity and noise level (20 m depth)

Correlation coefficient = 0.6555 Correlation coefficient = -0.1668

Correlation between current velocity and noise level (40 m depth)

Correlation coefficient = 0.6303 Correlation coefficient = -0.4576

Correlation between current velocity and noise level (52 m depth)

Correlation coefficient = -0.3027 Correlation coefficient = -0.0248

Summary

A self-recording hydrophone was newly developed to use for measurement of low-frequency ocean noise.

Low-frequency noise at a site of the South Sea of Korea was measured by using the self-recording hydrophone and conventional cabled hydrophones.

The self-recording hydrophone is superior to the conventional cabled hydrophone to measure low-frequency underwater noise when in particular water flow is strong.

Thank you!