The Subjective Analysis of Wheel-Rail Squealing Noise by Modification of the British Standard BS 4142:2014

This paper shows explicitly a calculation method for the case of squeal noise referring to the effect of signal to noise (S/N) ratio on speech intelligibility. This methodology is useful also in other cases of environmental noise. The British Standard BS 4142:2014 is a method for rating noise levels by comparing the rating level of the specific noise source with the background noise. It includes some corrections as compared with its older version, but it does not consider properly the difference in spectral contents of both background noise and the examined specific noise. We apply a modified approach, developed by this author in ASA meetings (Providence, 2014, Salt Lake City, 2016). It considers the influence of the spectrum of the intruding noise corrected by a scale that depends on the S/N ratio. It shows that the S/N influence on speech intelligibility and the influence of environmental background noise on the effect of a specific noise source on people may have a common correction scale. This statement needs verification by expert psycho-acousticians. Our measurements suggest that the human brain uses flexibly, the same scale, in both speech and noise, concerning the effect of S/N ratio on their perception.