In this study, experiments were conducted to determine the influence of vibration on loudness perception.

The audio-tactile loudness illusion was found: Sounds were perceived louder, when accompanied by vibrations.

This effect can be used, e.g. in discotheques or cars to reduce bass level, while simultaneously increasing the perceived sound quality.

Vertical whole-body vibrations were produced using an individually calibrated electro-dynamic shaker. A pair of closed dynamic headphones was used for audio reproduction.

A loudness matching experiment was carried out with 28 participants. In this experiment, sinusoidal sounds were presented in the absence and presence of simultaneous vibrations. Participants had to match the level of the acoustic stimuli while ignoring the tactile stimulation.

The loudness matching experiment was carried out for four sinusoidal tones, at the frequencies of 10, 20, 63 and 200 Hz. Three different vibration levels (4, 8 and 12 dB above the vibration threshold for each participant) were used to study the influence of the vibration amplitude.

Results indicate that whole-body vibration had a significant influence on loudness perception. When an acoustic stimulus was accompanied by vibration, the level of the acoustic stimulus was perceived one decibel higher on average. Taking into account, that the dynamic range of the auditory system decreases with decreasing frequency, a small increase in sound pressure level can change the perceived loudness considerably.

Want to know more? A detailed discussion and experimental data can be found in the following publications.

PDF logo Merchel, S., Schwendicke, A., and Altinsoy, M.E. (2011). Feeling the sound: audio-tactile intensity perception, in Proceedings of 2nd Polish-German Structured Conference on Acoustics, The 58th Open Seminar on Acoustics, Jurata, Poland.
PDF logo Altinsoy, M.E. & Merchel, S. (2011). Application of Audiotactile Intensity Interaction on Touch-Screens, in Proceedings of the EAA Forum Acusticum 2011, Aalborg, Denmark.
PDF logo Merchel, S., Altinsoy, M.E. & Leppin, A. (2010). Multisensorische Interaktion im Fahrzeug: Audio-Taktile Intensitätswahrnehmung. in Proceedings of the DAGA 2010 - 36th German Annual Conference on Acoustics, Berlin, Germany.
Link Merchel, S., Leppin, A. & Altinsoy, M.E. (2009). Influence of Whole Body Vibrations on Loudness Perception, in Proc. of the 16th Int. Congress on Sound and Vibration, ICSV 2009, Krakow, Poland.