Thanks for tips Vic. I hadn't realised that the slider on the left sets the recording threshold so now can see results on the plot too. The pulsing effect at ELF resembles the same response I mentioned earlier on the files that are no longer on here. I searched for them on my old disks but no joy. I will try I and get some time in on this utility- as it is easy to use, and actually deceptively sensitive, at the frequencies of interest to us here.
On Dec 14, 12:22 am, Vic <[email protected]> wrote: > One real simple test I did that proved it was a real noise: Stand in > your open patio door, one foot outside, one foot inside. Swing your > head and body, so that it's outside for a couple of seconds, then do > the opposite. It's generated outside, then gets in your house wiring. > > Second simple and free test: Go find a 138KV overhead electricity > transmission line, 3-phase (6 cables), 3 copper (green probably and > the live), 3 aluminum ( grey). Stand under them looking along them. If > the Hum is going you will hear it in front of you and behind you. Walk > and the Hum appears to stay at the same distance from you in both > directions as you do. > > 3rd simple and free test: Download AP Tuner 3.8 (It's freeware that > you pay for if you like it). Install and run it on a laptop computer > with a built in mic. you will see your 58Hz Hum - It bounces back and > forth between B1 and Bflat1. You may have to go into "Sound" in > Control Panel (Windows) and up the mic boost (volume) by 10 or 20dB. > but you'll pick it up every time! > > It's a real noise, you hear it normally with your dBC hearing > capability. > > On Dec 13, 5:23 pm, "R.D." <[email protected]> wrote: > > > > > > > > > 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) 965-8516http://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]. 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