Bif Posted December 17, 2014 Report Share Posted December 17, 2014 As far as reducing hearing loss, ANR does not help as the wave lengths of noise are still hitting your eardrum but the anr system transmits the opposite wavelength thus you brain does not register a "new" noise. Sorry Skully, I was with you right up until here. ANR reduces hearing loss exactly because of the phenomenon you describe (initially): the system generates an opposite signal which cancels (to the best of its ability) the original noise by destructive interference. It's not a case of the system doubling the amount of sound waves coming in, just in a clever way that tricks your brain... the system is physically reducing the strength/amplitude of the incoming sound the same way that 2 wave patterns crossing in water will produce flat spots where they oppose. I expect the reason it doesn't work for some people, or seems to make things worse even, is that the system is not perfect and/or is not applied properly. It boil down to a microphone picking up all the noises coming in and then a computer chip decided which noises to cancel and how, so it obviously won't work with sudden or randomly fluctuating noises. But that's why it works so well with steady noises like airline cabins etc, though I can't account for the difficulty with turbines... maybe you're right and the frequency is just too high for the system to a) pick up, or produce a low enough tone to effectively cancel. Anyway, that's just me armchair-scientisting... I could have forgotten a thing or two since 1st year physics hahaha. I'm going to be lazy and cite wikipedia: http://en.wikipedia.org/wiki/Active_noise_control "A noise-cancellation speaker emits a sound wave with the same amplitude but with inverted phase (also known as antiphase) to the original sound. The waves combine to form a new wave, in a process called interference, and effectively cancel each other out - an effect which is called phase cancellation. Modern active noise control is generally achieved through the use of analog circuits or digital signal processing. Adaptive algorithms are designed to analyze the waveform of the background auralor nonaural noise, then based on the specific algorithm generate a signal that will either phase shift or invert the polarity of the original signal. This inverted signal (in antiphase) is then amplified and a transducer creates a sound wave directly proportional to the amplitude of the original waveform, creating destructive interference. This effectively reduces the volume of the perceivable noise." But Iceman's link covers it well too Occupational Health and Safety article http://ohsonline.com/Articles/2007/06/Active-Noise-Reduction.aspx?m=1 1 Quote Link to comment Share on other sites More sharing options...
Bif Posted December 17, 2014 Report Share Posted December 17, 2014 I can't account for the difficulty with turbines... maybe you're right and the frequency is just too high for the system to a) pick up, or produce a low enough tone to effectively cancel. Going to correct myself here. High frequency sound is not cancelled out by low frequency sound. But, quoting wikipedia again: "Active noise canceling is best suited for low frequencies. For higher frequencies, the spacing requirements for free space and zone of silence techniques become prohibitive. In acoustic cavity and duct based systems, the number of modes grows rapidly with increasing frequency, which quickly makes active noise control techniques unmanageable. Passive treatments become more effective at higher frequencies and often provide an adequate solution without the need for active control." ... whatever that means Quote Link to comment Share on other sites More sharing options...
skullcap Posted December 17, 2014 Report Share Posted December 17, 2014 No worries Bif, I cannot for the life of me find any verification to back up my statement thus just old. It seems strange anr does not work for some people. But to be honest I won't use it for the same reason freewheel describes with their engine failure. Quote Link to comment Share on other sites More sharing options...
Bif Posted December 17, 2014 Report Share Posted December 17, 2014 Oh totally. Each person will make their own decision based on their personal assessment of risk of hearing loss vs risk of not hearing an impending failure. Just like every pilot will make his own choice to wear a helmet or not, or a flight suit, or what have you... Quote Link to comment Share on other sites More sharing options...
Iceman Posted December 17, 2014 Report Share Posted December 17, 2014 Ya we are getting old Freewheel haha. I wouldn't be so quick to shun ANR though especially like the Bose A20 I use. My hearing has improved in the 2 months I've had it (dont have to crank the TV volume so high) and I am only half as tired as I used to be at the end of da day. As far as hearing the compressor that is still the dominant sound with my ANR (nailed it RE C20R). Next would be the 2 per rev and swish from the blades. I'm certain I would hear a bang from the compressor. I still jump when a pass drops something on the floor behind me. Pretty sure the N1 would drop fairly rapid as a warning, bang or not. Like mentioned earlier the best is to borrow a set and give it a try you might be surprised. Quote Link to comment Share on other sites More sharing options...
flingwinger Posted December 17, 2014 Report Share Posted December 17, 2014 Anr didn't work for me either, ears ringing and headaches after a long day. Now run custom moulded CEP's and am very happy. Quote Link to comment Share on other sites More sharing options...
twinstar_ca Posted December 17, 2014 Report Share Posted December 17, 2014 so a bit of a hijack.. i got one of the helmets from HAWCs and I'm wondering if there is an adapter cord that i can get that will convert from the ANR connection to a civilian machine... you can see the cord end on the "marketplace" thread under used alpha helmets... Quote Link to comment Share on other sites More sharing options...
Freewheel Posted December 18, 2014 Report Share Posted December 18, 2014 Oh totally. Each person will make their own decision based on their personal assessment of risk of hearing loss vs risk of not hearing an impending failure. Just like every pilot will make his own choice to wear a helmet or not, or a flight suit, or what have you... Exactly Ya we are getting old Freewheel haha. I wouldn't be so quick to shun ANR though especially like the Bose A20 I use. My hearing has improved in the 2 months I've had it (dont have to crank the TV volume so high) and I am only half as tired as I used to be at the end of da day. As far as hearing the compressor that is still the dominant sound with my ANR (nailed it RE C20R). Next would be the 2 per rev and swish from the blades. I'm certain I would hear a bang from the compressor. I still jump when a pass drops something on the floor behind me. Pretty sure the N1 would drop fairly rapid as a warning, bang or not. Like mentioned earlier the best is to borrow a set and give it a try you might be surprised. To be clear I wasn't shunning ANR; as stated I own a Bose. I just think my point is something that should be considered. I have seen the ANR conversation pop up several times over the years, and it's rarely discussed. The sound of a fire extinguisher hitting the floor (inside the cabin) is something you literally feel through your body. There are many sounds outside the cabin you may not hear. Not all sounds that could indicate an impending failure are a loud bang. FYI I'm not that old...I haven't noticed any significant hearing loss yet Quote Link to comment Share on other sites More sharing options...
skullcap Posted December 18, 2014 Report Share Posted December 18, 2014 hmm, you don't seem to listen to well so maybe get it checked! Ha ha. Quote Link to comment Share on other sites More sharing options...
Freewheel Posted December 18, 2014 Report Share Posted December 18, 2014 hmm, you don't seem to listen to well so maybe get it checked! Ha ha.If you ask my wife (or TC Ontario Region for that matter), she'll likely agree with ya... over the years of listening to nonsense I have learned to ignore it...kinda like my own personal built in ANR . There is a big difference between "Hearing" and "Listening" Quote Link to comment Share on other sites More sharing options...
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