Detectability of auditory warning signals in the ambient noise of Dutch train cabins

Locomotive engineers need to detect auditory warning signals for safe and effective job performance. We measured the levels and spectra of the warning signals and noises present in Dutch train cabins to evaluate the effectiveness of these signals. Audio-recordings were made in six train types during normal operation. Signal detectability was estimated using the Detectsound software and compared against ISO 7731. Signal detectability was also measured in six normally-hearing individuals in a laboratory setting. Signal levels ranged between 68 and 84 dBA. Noise levels ranged between 53 and 77 dBA. The acoustical requirements for signal detectability were not met in multiple driving conditions, especially at higher speed. Sufficient signal-to-noise ratio's were achieved in the laboratory measurements, but difficulties can be expected in unfavourable driving situations or when the engineer suffers from hearing loss. Acoustical, environmental, or work modifications might be required to prevent situations with insufficient audibility in hearing-impaired engineers. Practitioner summary: The audibility of the warning signals in Dutch trains was evaluated by comparing signal and noise spectra. The results showed that sufficient audibility is not always guaranteed. Under laboratory conditions, normally-hearing individuals could compensate for the suboptimal acoustic circumstances, but acoustical, environmental, or work modifications might be required to prevent situations with insufficient audibility in hearing-impaired engineers.