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Background sound |
| Sound from all sources other than the particular sound that is of interest (e.g., the sound other than that being measured, the sound other than the speech being listened to, etc.). |
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Bandwidth (hz) |
| The width, in hertz, of a filter used in acoustical measurments. The width can be an octave, or larger, a one-third octave, a fixed percentage of the frequency, or a constant number of frequencies. |
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Base line audiogram |
| A valid audiogram obtained within 6 months of an employee's first exposure to 90 DSA (or higher) time-weighted average noise level. This is the audiogram against which subsequent audiograms are compared to determine the Standard Threshold Shift. The base line audiogram may be replaced if a subsequent audiogram indicates better hearing levels. |
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Base line sound level (dB) |
| Measured sound level prior to the implementation of any noise mitigation project. The base line sound level is the ambient sound level plus the source sound emission. |
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Beat frequency |
| Two (or more) pure tones almost equal in frequency so that the sound level of the combined pure tones varies with time at a frequency which equals the difference in frequency between the two tones. |
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Breeching |
| The duct work used to convey the combustion products from the boiler to the chimney. |
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