Hydrophones

Over the years, acousticians at NMFS have utilized three different hydrophone makers: APC- this consisted of a piezo-electric cylinder that was hand soldered to the wires to create a hydrophone. Sensistivity was uncharacterized and subject to the solderer’s capability. This is the least desirable of the hydrophone types NMFS uses.

Reson- these hydrophones have the best response curve in terms of being flat across a broad range of frequencies (X-xx) but they are less sensitive relative to HTIs

HTI- this is the hydrophone type that is currently preferred by the NMFS science centers. While it does not have a flat frequency response, a few models have been measured by Jay Barlow such that the response curve is known. The model types that are used are:

want to put images of these hydrophones before each number so that one knows what they look like

1. HTI-96-Min: these are used in real-time towed hydrophone arrays (flexible tube). Peak sensitivity is at 96 kHz

2. HTI-99-HF: these were used in drifting recorders but are starting to be phased out. what is the positive/negatives of using this hydrophone type

3. HTI-92-WB: used in drifting recorders and can be used in the SoundTrap towed array (just 1). These are the most sensitive HTI hydrophones and also the most expensive, but give you the best detection ranges