VT USA-168A/B Real Time Underwater Sound Analyzer Manual Rev. 1.5
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where the Standard 0dB Reference for sound pressure level in air is 20 µPa (i.e. 2e-005 Pa)
and that in water is 1 µPa (i.e. 1e-006 Pa). If the actual sensor sensitivity is used, then the
standard 0dB reference should be entered into the “0dB Reference Vr” edit box. For
example, the following two methods are equivalent.
VT USA-168A
Method 1: [0dB Reference Vr] = 5.623e-009 (V) and [Sensor Sensitivity] = 1 V/V
Method 2: [0dB Reference Vr] = 1e-006 (Pa) and [Sensor Sensitivity] = 0.005623 V/Pa
VT USA-168B
Method 1: [0dB Reference Vr] = 1.585e-009 (V) and [Sensor Sensitivity] = 1 V/V
Method 2: [0dB Reference Vr] = 1e-006 (Pa) and [Sensor Sensitivity] = 0.001585 V/Pa
The sensitivity of a hydrophone is usually specified in dB with reference to 1V/μPa, it can be
converted to V/Pa as follows:
Sensitivity (V/Pa) = power (10, Sensitivity (dB)/20) × 10
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For example, the nominal sensitivity of the hydrophone in VT USA-168A is -165dB, i.e.
0.005623 V/Pa. The nominal sensitivity of the hydrophone in VT USA-168B is -176dB, i.e.
0.001585 V/Pa. The nominal sensitivity of the old version of VT USA-168A is -180dB, i.e.
0.001 V/Pa. The nominal sensitivity of the old version of VT USA-168B is -192dB, i.e.
0.0002512 V/Pa.
1.6 Most Frequently Used Measurement Settings
Multi-Instrument bundled with VT USA-168A/B comes with many pre-configured panel
setting files. This saves you time to configure various parameters for some frequently
performed measurements by yourself. You can load these panel setting files via
[Setting]>[Load Panel Setting]. Furthermore, up to 20 most frequently used panel setting
files can be configured in the Hot Panel Setting Toolbar (The third toolbar from the top) via
[Setting]>[Configure Hot Panel Setting Toolbar]. You can load one of them by a single
mouse click. Two panel setting files are preconfigured in this toolbar. They are:
(1)
Home: Default Setting
The factory default panel setting. It is equivalent to the [File]>[New] command.
(2)
OCT3: 1/3 Octave Analysis
1/3 octave band spectrum analysis instead of narrow band FFT spectrum analysis will be
perform on the sampled data.
1.7 Using Hydrophone with Batteries or an External Power Supply without
a Computer
The XLR-to-USB sound card can be powered by two HR6 (1.2V) or LR6 (1.5V) AA size
batteries, or an external 5V DC power supply (e.g. a mobile USB battery) if the “POWER
