Sound propagation and audibility of train horns

Abstract

Horn sound levels and sound propagation along railway tracks were investigated after track workers reported that some newer trains have quieter horns than older trains. Sound levels from a static horn above a test track decayed by 6 dB per doubling of distance, but only up to about 30 or 50 metres depending on the horn height. At greater distances the level decayed by approximately
12 dB per doubling. At 400 metres, the sound level from a horn 2.5 to 3.0 metres above the ground was about 10 dB higher than the level from the horn 0.5 metres above the ground, although the levels at 25 metres were the same. The effective range of a horn depends on its height. At two mainline sites the mean attenuation rates beyond 90 metres were 10.7 and 9.2 dB per doubling of
distance. At one site, horn sound levels were highly correlated with distance. At the other, with newer trains, horn levels were poorly correlated, suggesting some variability in horn sound levels at source, or moment to moment variability in sound propagation. Track workers’ ratings of the audibility of the horns were compared to horn levels as recommended by Detectsound and by ISO 7731

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Identifiers

ORCID for Martin Toward: orcid.org/0000-0001-7334-4355

ORCID for David Thompson: orcid.org/0000-0002-7964-5906

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