Underwater Sound from the RTC Pier { Underwater Acoustics Research Group }

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Sounds of the Plainfin Midshipman

The Plainfin Midshipman (Porichthys notatus) has been known for its loud, rumbling humms ever since it was identified as the source of these noises by John McCosker, of the California Academy of Science. Residents of the Sausalito houseboat community were losing sleep due to a raspy continuous drone, at a frequency of about 100 Hz (A below C below Middle C, for you tuba players). This sound can be heard at any time of day, but the midshipman expecially favors the wee hours between midnight and 6:00 AM.

The behavior and vocalizations of the midshipman have been studied for years in the laboratory of Andrew Bass, at Cornell University.

The Romberg Tiburon Center is located on the North SF Bay, with a 200-foot pier extending into deep water. A hydrophone deployed from the end of the pier monitors underwater sounds, 24 hours a day. Some interesting midshipman sounds are shown below.

HUM Here a group of toadfish hum for fifteem minutes, at about 98 Hz. In the Flash animation, listen for a ratchet call and a series of toots, just at the end. [MP3 for minute 2 | blowup of minute 2 | FLASH

RATCHET In this 15-minute interval there are a number of ratchet calls (or "growls"), over a background of continuous humming. This call is thought to be an "agonistic" call, used to defend territory. [MP3 for minute 5 | blowup of minute 5 | FLASH

TOOTS (or grunts). This spectrogram is filled with short toots, more or less at the humming frequency, repeated about once per second. This is also said to be an "agonistic" call. [MP3 for minute 6 | blowup for minute 6| FLASH]
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