Low-Frequency Noise Impulses from Explosions

For military noise evaluation, noise impulses from explosions of 60 g – 2 20 kg equivalents of TNT (trinitrotoluene) were measured at distances of 10 – 300m. Noie and air-blast sensors (an LC-33 pencil gauge, a Kistler 6103 detonation sensor, B&K 8103 and B&K 8105 hydrophones and a B&KI 4136 microphone) were used for the measurements. The peak values, A-durations, impulse energies and frequency transforms were usually analysed from the tape-recorded signals (waveform analyser DATA 6000). At a distance of 100m, the means of the 60 g and 20 kg explosions were as follows: 144 dB and 163 dB for the peak values, 4.0 ms and 13.0 ms for the A-durations, 250 Pa ² s and 51 kPa ² s for the impulse energies, and 1200 Hz and 15 Hz for the most prominent frequencies, respectively. The peak levels decreased 5–8 dB when the distance was doubled. A graphic nomogram was formed from the peak values for training, safety, and noise control purposes.