The effects of low frequency sound on the levels of activation

The paper summarises the research data showing how low frequency sound affects the level
of activation in humans. Activation levels were measured with the use of the self-assessment
questionnaire, known as the Activation-Deactivation Adjective Check List (AD ACL). The research
program involved three independent stages and three types of acoustic stimuli were
applied. The acoustic stimulus applied in the first stage had frequency $f = 7$ Hz, sound pressure
level SPL = 120 dB (HP). In the second stage participants were exposed to an acoustic
stimulus $f = 18$ Hz, sound pressure level SPL = 120 dB (HP). In the third stage a acoustic
stimulus was applied $f = 40$ Hz, sound pressure level SPL = 110 dB (HP). The exposure
time in each experiment was constant (20 min). Results indicate a statistically significant
increase of the deactivation – sleep effect following the low-frequency sound exposure.