Identifying diesel engine sounds

Naval ratings were given the task of identifying the sounds of three lorry diesel engines at running speeds of 1000, 2000 and 3000 rev/min. The physical signal was varied by adding thermal noise and by multiplying all frequencies by factors of 1, 2, 4 and 8. The experimental variables were knowledge of results, amount of cueing, and the meaningfulness of the identifying names. Meaningfulness consisted either of code names or of the real names plus a description of the physical characteristics of the engine. Where real names were in use, identification was more accurate even with frequency multiplication. Engine types were identified better than engine rev/min. The accuracy of engine identification decreased as the noise masking increased and as the frequency multiplications changed from × 1 to ×2 to ×8 to ×4. However, when noise masking was absent, engine identification at the ×8 speedup yielded scores equal to ×1 and ×2. The rev/min identifications were all equivalent except at ×4 in noise, which always gave the lowest score.