Abstract Studies of sound propagation in the shallow waters of the Bristol Channel were carried out between 1967 and 1969, with a systematic coverage of the seasons. Acoustic signals were transmitted and monitored by fixed bottom-laid transducers, the main path lengths being 17, 23 and 137 km. Transmissions consisted of a sequence of tone pulses, varying from 0·3 to 4·5 kHz. Both symmetrical and asymmetrical patterns of modal interference were seen, and it was deduced that at 23 km the number of effective modes was proportional to frequency. Seasonal changes were not marked at 17 and 23 km, but at 137 km there was about 30 dB extra loss in the summer. The latter is thought to be mainly due to fish attenuation, with a significant contribution from summer layering effects at the lower frequencies only. Five other types of amplitude fluctuation were seen, which it is hoped to report later.
[1]
D. E. Weston.
Guided Propagation in a slowly varying Medium
,
1959
.
[2]
W. H. Thorp.
Analytic Description of the Low‐Frequency Attenuation Coefficient
,
1967
.
[3]
D. E. Weston,et al.
Studies of sound transmission fluctuations in shallow coastal waters
,
1969,
Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.
[4]
D. E. Weston,et al.
Experiments on time-frequency interference patterns in shallow-water acoustic transmission
,
1969
.
[5]
W. H. Thorp.
Deep-Ocean Sound Attenuation in the Sub- and Low-Kilocycle-per-Second Region
,
1965
.
[6]
D. E. Weston,et al.
Interference of wide-band sound in shallow water
,
1972
.