Acoustics

Noise Exposure

Occupational noise dose and 8-hour time-weighted average from a list of exposure segments or dosimeter readings under the OSHA permissible exposure limit of 29 CFR 1910.95 (90 dBA criterion, 5-dB exchange rate, 90 dBA threshold for the PEL and 80 dBA for the hearing-conservation dose), the NIOSH recommended exposure limit of Publication 98-126 (85 dBA, 3-dB exchange rate) or the ACGIH TLV, with every reference duration written out, the equivalent continuous level, the remaining permitted time at the current level and the margins to the action level and the limit; the protected level under a hearing protector from its NRR with the OSHA 50 % derating, the NIOSH 25 / 50 / 70 % derating by protector type, dual protection and the C-weighted method of Appendix B; the A- and C-weighted overall levels of an octave-band spectrum with the IEC 61672 weightings, the octave-band (long) method of protector attenuation and the NRR recomputed from attenuation data as in 40 CFR 211.207; the decibel sum of several sources with inverse-square or line-source distance attenuation and a Maekawa barrier; and a reverberant-room estimate (Sabine time, room constant, critical distance). The default day is the OSHA Technical Manual example (95 dBA for 2 hours and 90 dBA for 3 hours: dose 87.5 %, TWA 89.0 dBA) with an NRR 29 protector, and the default spectrum is the manual's A-weighting example (105.5 dBA).

1 worked example reproduced, listed on the tool page.

Room Acoustics and Noise Control

Three sub-tools on one page. Room reverberation: the octave-band absorption of every surface (coefficients from the UFC 3-450-01 table of building materials or entered), people and chairs, air absorption by the ISO 9613-1 closed form, Sabine, Eyring and Millington reverberation times, room constant, Schroeder frequency, the absorption to add for a target reverberation time and the treatment area that gives it, and the direct-plus-reverberant level of a source of known sound power (critical distance, NC rating against the UFC design goal). Sound transmission: the mass law and coincidence dip of a single panel, the composite transmission loss of a wall with a door and openings, the noise reduction between rooms by the UFC equation and the Sabine form, the receiving-room spectrum, and a Sound Transmission Class by the ASTM E413 contour rule. Noise criteria: NC and RC Mark II ratings of an entered spectrum with its A-weighted level and speech interference level, equivalent and day-night levels of a 24-hour history, the Maekawa barrier insertion loss, and outdoor propagation (spreading, air absorption, anomalous excess attenuation, ground or woods, barrier, exterior wall) to the indoor spectrum of a neighbour, reproducing the cooling-tower example of UFC 3-450-01. The default room is a 30 x 20 x 10 ft office (illustrative).

1 worked example reproduced, listed on the tool page.

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