.SGY files were recorded with the onboard parasound system. The Atlas PARASOUND system P70 uses the parametric effect, which occurs when very high (finite) amplitude sound waves are generated. If two waves of similar frequencies are generated simultaneously, also the sum and the difference of the two primary frequencies are emitted. For the PARASOUND System, 18 kHz is one fixed primary frequency, which is generated by a transducer of ~ 1m length within a beam of 4.5°. The second primary frequency can be varied between 18.5 and 24 kHz, resulting in difference frequencies from 0.5 to 6.0 kHz. The system treats three signals separately: the primary high frequency signal (18 kHz; PHF), the secondary low frequency signal (selectable 0.5 to 6.0 kHz; SLF) and the secondary high frequency (selectable 36.5 to 42 kHz; SHF). We selected 4 kHz as SLF and 40 kHz as SHF. The segy files attached here represent the SLF signal.