Being Heard in the Market: How Far a Voice Carries Against Market Noise, What a Day of Shouting Costs, and What a Small Amplifier Changes

A market vendor must be understood, not merely heard, across a stall counter. This study models unaided speech against stated market ambient noise of 70, 75, 80, and 85 dBA, using free-field spreading from stated voice levels at 1 m (normal 60, raised 66, loud 72, shout 78, and maximum sustained shout 82 dBA), a criterion that speech exceed the ambient by 6 dB at the listener, and a Lombard rise of 0.5 dB in voice level for each decibel of noise above 45 dBA. At 70 dBA a shout at 78 dBA remains intelligible only to 1.259 m, and normal speech only to 0.158 m. At 80 dBA the distance for a shout falls to 0.398 m, and the voice level required for conversation at 1.0 m is 86.0 dBA, which is 4.0 dB above the stated maximum sustained shout and 8.5 dB above the Lombard voice of 77.5 dBA. At 85 dBA the required level at 1.0 m is 91.0 dBA. A vendor phonating for 2.4 hours of an 8-hour day at the level required at 80 dBA accumulates 955.5 normal-voice hour equivalents of vocal dose, compared with 2.4 at normal voice. A personal voice amplifier priced at $15.00, with a stated gain of 12 dB, reduces the speaker's own level needed at 80 dBA from 86.0 to 74.0 dBA and the dose by a factor of 15.85, to 60.3 equivalents, and it lets a raised voice of 66 dBA reach 1.259 m at 70 dBA. The amplifier extends comfortable working distance at moderate noise; it does not make conversation at 1 m possible by a comfortable voice at 85 dBA. SIMULATED, NOT MEASURED.