For coupling SoundTrap ST300 hydrophones to a 1″ pistonphone.
Verified to work with the GRAS 42AA pistonphone with 1″ adapter. May also work with other 1″ pistonphones.
Note that the coupler’s internal volume is not standard, meaning the applied sound pressure will vary from the nominal pistonphone output. It is therefore necessary to measure the actual SPL using a reference instrument. A 1/2″ side port is provided for this purpose.