Table 1. Absolute amplitude levels and SNRs of words played at each distance of listening.

Distance (meters)	11	13	15	17	19	21	23	25	27	29	31	33
Level (dB(A))	44.5	43	41.8	40.7	39.7	38.9	38	37.3	36.7	36	35.5	34.9
SNR (dB)	−8.8	−10.3	−11.5	−12.6	−13.6	−14.4	−15.2	−15.9	−16.6	−17.2	−17.8	−18.4

With a reference mean value of 65.3 dB(A) for words at 1 meter from the source and a natural background noise produced at 41.6 dB(A).