Low-frequency sounds are difficult for humans to hear, but new research indicates that despite their lack of perception, these signals trigger detectable micromechanical responses by the nerve cells in the inner ear. Researchers at the Ludwig Maximilian University of Munich (LMU) in Germany report that sounds at frequencies below 100 Hz, previously thought to be undetectable, do evoke a response. These low-frequency signals are common in everyday life and include signals emitted from air conditioners and heating pumps.
The researchers at LMU used experimental subjects with normal hearing. These subjects were exposed to low-frequency tones for one minute and spontaneous otoacoustic emissions (SOAEs) were measured using specialized microphones in the subject’s inner ear. Results indicate that the ear’s cochlea is stimulated for longer than even the exposure to the low-frequency. For example, some subjects’ SOAEs had slow oscillations for up to 120 seconds, 30 seconds longer than the exposure.
The study paves the way for further investigations into the possible dangers of low-frequency sounds and highlights the question the role of low-frequencies in creating or contributing to noise-induced auditory hearing damage.
Source: Science Daily