NAUTA scientific

sensing the world

A simple comparative test

Frequency response of two hydrophones and a test signal on the uRec384k recording board

In January 2021 we performed a comparative test of a new production batch of the uRec84k recording board.

The test was aimed at comparing the frequency response of a test signal and two hydrophones.

The signal used was output by a Rigol DG812 signal generator.

The signal was recorded under three conditions:

  • direct feed to the recording board
  • played into a small test tank and detected using an Aquarian Audio H2c hydrophone
  • played into the same small test tank and detected using an Aquarian Scientific AS-1 hydrophone, with no preamplifier other than the internal settable gain on the recording board.
The tank reflections can greatly impact on the received levels, together with the sensor position, in the small tank.
These tests are usually made using extremely short impulsive signals, while we decided to use long frequency sweep in these tests.
We moved up and down the sensor in the tank, in order to get the highest signal level.
Our main interest was not to estimate sensitivity, but to cross check the frequency response of the two sensors, after having a characteristic frequency response of the board itself, with a direct feed to the board from the generator.

A comparative table

Files have been analyzed using the spectral analysis in Adobe Audition.
The intensities at different frequencies, have been measured and compared among the two sensors.
Here is the resulting table.

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