THE EFFECTS OF BACKGROUND NOISE UPON PERCEIVED NOISINESS
Abstract
Cross modality tests, in which subjects matched the apparent intensity of a 100 Hz vibration applied to the fingertip to the noisiness of one-third octave bands of noise with center frequencies of 125 Hz, 1000 Hz and 4000 Hz, have been conducted to measure the effects of background noise upon the judged noisiness of the bands of noise. The tests have indicated that the growth function for noisiness behaves somewhat like a modified power function of the form psi = k (I to the n power - (I sub o) to the n power) where psi is noisiness, I is the intensity of the stimulus, Io is the threshold intensity for the stimulus in a given background noise and k and n are constants which depend upon the frequency of the stimulus noise band. On the basis of the results of the cross modality tests, a calculation scheme has been developed to account for the effects of background noise in the perceived noise level calculation. The calculation procedure reduces, differentially, the sound pressure level of each third octave band of the judged noise by an amount dependent upon the signal- noise-to-background-noise ratio in that frequency band. For signal-noise-to- background-noise ratios of greater than 65 dB, the band correction is equal to zero. However, preliminary calculations have shown that for realistic background spectra and signal-noise-to-background-noise ratios of 40 dB, the effect upon the perceived noise level of a judged noise, as predicted by the calculation scheme, is approximately 3 PNdB.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1967
- Accession Number
- AD0663902
Entities
People
- David C. Nagel
- Hugh J. Parry
- John E. Parnell
Organizations
- BBN Technologies