Document ID: chunk:federal_register_of_legislation:F2024L01024:front:0:p185
Version: federal_register_of_legislation:F2024L01024
Segment Type: other
Provision Reference: 
Character Range: 536985–539860

'flexible piezoelectric composite' sensing elements consist of piezoelectric ceramic particles or fibres combined with an electrically insulating, acoustically transparent rubber, polymer or epoxy compound, where the compound is an integral part of the sensing elements.
3. For the purposes of 6A001.a.2.a., 'hydrophone sensitivity' is defined as twenty times the logarithm to the base 10 of the ratio of rms output voltage to a 1 V rms reference, when the hydrophone sensor, without a pre‑amplifier, is placed in a plane wave acoustic field with an rms pressure of 1 µPa. For example, a hydrophone of ‑160 dB (reference 1 V per µPa) would yield an output voltage of 10‑8 V in such a field, while one of ‑180 dB sensitivity would yield only 10‑9 V output. Thus, ‑160 dB is better than ‑180 dB.
6. A. 001. a. 2. b. Towed acoustic hydrophone arrays having any of the following:
                  Technical Note
                  For the purposes of 6A001.a.2.b., hydrophone arrays consist of a number of hydrophones providing multiple acoustic output channels.
1. Hydrophone group spacing of less than 12.5 m or 'able to be modified' to have hydrophone group spacing of less than 12.5 m;
2. Designed or 'able to be modified' to operate at depths exceeding 35 m;
Technical Note:
For the purposes of 6A001.a.2.b.2., 'able to be modified' in 6A001.a.2.b. means having provisions to allow a change of the wiring or interconnections to alter hydrophone group spacing or operating depth limits. These provisions are: spare wiring exceeding 10% of the number of wires, hydrophone group spacing adjustment blocks or internal depth limiting devices that are adjustable or that control more than one hydrophone group.
6. A. 001. a. 2. b. 3. Heading sensors specified by 6A001.a.2.d.;
4. Longitudinally reinforced array hoses;
5. An assembled array of less than 40 mm in diameter; or
6. Not used;
7. Hydrophone characteristics specified by 6A001.a.2.a.;
8. Accelerometer‑based hydro‑acoustic sensors specified by 6A001.a.2.g.;
6. A. 001. a. 2. c. Processing equipment, specially designed for towed acoustic hydrophone arrays, having "user‑accessible programmability" and time or frequency domain processing and correlation, including spectral analysis, digital filtering and beamforming using Fast Fourier or other transforms or processes;
6. A. 001. a. 2. d. Heading sensors having all of the following:
6. A. 001. a. 2. d. 1. An "accuracy" of better than 0.5°; and
2. Designed to operate at depths exceeding 35 m or having an adjustable or removable depth sensing device in order to operate at depths exceeding 35 m;
                       N.B.: For inertial heading systems, see 7A003.c.
6. A. 001. a. 2. e. Bottom or bay cable systems, having any of the following:
1. Incorporating hydrophones specified by 6A001.a.2.a.; or
2. Incorporating multiplexed hydrophone group signal modules