FYI, I hope to hear back from Lin on my observations and questions. There is a mechanism where the ear can produce its own feedback sound.
[email protected] Low-frequency modulation of distortion product otoacoustic emissions in humans Lin Bian and Nicole M. Scherrer Auditory Physiology Laboratory, 3430 Coor Hall, Department of Speech and Hearing Science, Arizona State University, Tempe, AZ 85287-0102 Contact Information: E-mail: [email protected], Tel: (480) 727-0650, Fax: (913) 965-8516 http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2612004/ Hi Lin, I think I am observing on a regular basis a otoacoustic emission at 58 Hz at my home in MD. Since in the ear isolation ear phones and shooting ear protectors seem to eliminate the hum sound, my guess is there is a real sound of a very low level penetrating my home and initiating the 58 Hz hum I hear often. Here are my latest observations, let me know what to try next. The hum seems to be louder in the center of the room and less near the floor. Bending over forward stops the hum. Moving the head quickly side to side (no) momentarily stops the hum. If a low hum noise comes on, like from my heat pump or refrigerator the hum is overcome by this sound but returns after it stops. Playing music partially stops the hum, but high frequencies above voice frequencies are less effective and bass sounds more effective. But with low volume music, the hum comes back between louder passages of music content. Quiet nights, the hum is heard outside, but real hum noise can also be heard as I live on the C&D canal and ships go by at random times. The ships are pretty quiet but some can be heard for miles as another more real hum and slowly subside. The hum can be heard in all rooms and the basement and in a closed car with the engine off. I have only noticed it at my residence and can no hear it at work. Other sources of low frequency noise can be heard in addition to the hum and can be directionally isolated. The hum is non-directional for the most part. So I am thinking the hum is real and either a outside source that my ears are amplifying and making more noticeable or there are some outside sources that are causing an otoacoustic resonance within both ears that will not dye out under typical conditions. Can you suggest any other simple tests I can try to figure out if there is an external source initiating this hum? I tried using a large 12 inch woofer as a microphone connected to the isolation ear buds and although tapping the woofer cone could be heard, no hum could be detected. Is there an inexpensive 58 Hz capable microphone available that I can connect to the noise isolating ear buds to determine if there is an outside sound source causing this hum? It would have to be capable of detecting sounds at 58 Hz that are about 1/2 to 1/3 the loudness of rubbing two fingers gently together at the ear. Thanks for any help with this, I do not remember hearing this type of regular and same intensity hum anywhere else I have been except for that week in Vermont on Mt Stowe. Sincerely, Ralph ---------------------- definitions: The fine tuning mechanisms involved in the normal processing of sound in the cochlea are non-linear, hence combination tones are generated inside the cochlea when a pair of low-level pure tones with neighbouring frequencies f1 and f2 is used as a stimulus. Their detection as sounds in the ear canal proves that they undergo backward propagation in the cochlea and through the middle ear, and the non-invasive measurement of the combination tone at 2f1-f2, called the cubic difference tone (CDT). Low-frequency modulation of distortion product otoacoustic emissions (DPOAEs) was measured from the human ears. In the frequency domain, increasing the bias tone level resulted in a suppression of the cubic difference tone (CDT) and an increase in the magnitudes of the modulation sidebands. Higher-frequency bias tones were more efficient in producing the suppression and modulation. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2612004/ -- You received this message because you are subscribed to the Google Groups "Hum Sufferers" group. To post to this group, send email to [email protected]. To unsubscribe from this group, send email to [email protected]. For more options, visit this group at http://groups.google.com/group/hum-sufferers?hl=en.
