Acoustics and physics
Octave band
Also known as octave bands, 1/3 octave band.
An octave band is a frequency range whose upper bound is twice the lower bound. Standard centre frequencies (in Hz) used for industrial-noise work are 31.5, 63, 125, 250, 500, 1000, 2000, 4000, 8000 and 16000. One-third octave bands subdivide each octave into three for higher resolution. Reporting SPL as a spectrum across these bands — instead of as a single broadband number — is the standard format for noise-exposure analysis under OSHA 29 CFR 1910.95 and EU Directive 2003/10/EC.
Why octave-band data matters for sonic horns
A 75 Hz sonic horn puts most of its energy into the 63 Hz octave band, with smaller amounts in adjacent bands from harmonic content. Exposure assessments at the operator station — and the design of any sound-attenuation enclosure — depend on knowing the spectrum, not just the broadband SPL. Hearing-protection rating (NRR / SNR) is also octave-band-dependent.
Related terms
Related terms
- FrequencyFrequency is the number of acoustic cycles per second, measured in hertz. Industrial acoustic cleaners operate at 12–30 Hz (infrasonic), 60–250 Hz (low) or 250–450 Hz (high).
- DecibelThe decibel is a logarithmic ratio used to express sound pressure, sound intensity and sound power. A 10 dB rise represents a tenfold rise in intensity.
- Sound pressure levelSPL is the logarithmic measure of sound pressure in decibels relative to a 20 µPa reference. Industrial sonic horns operate at 140–180 dB SPL.
- OSHA 29 CFR 1910.95OSHA 29 CFR 1910.95 sets US occupational noise exposure limits. The action level is 85 dBA TWA; the permissible exposure limit is 90 dBA TWA. Calculated from time-weighted average exposure.
- EU Directive 2003/10/ECEU Directive 2003/10/EC sets noise-exposure limits for EU workplaces. Lower action 80 dBA, upper action 85 dBA, exposure limit 87 dBA, all daily averages.