Proven Radio/Intercom system?

[chook]

Hi Bones. I"m really worried that from your description you are heading for severe hearing damage - and that will be permanent! You need to get a comfortable sound level on the ground - the same level that you would normally listen to say the radio in the car while it"s stationary. Any level above that is only compensating for externally generated noise. Your current situation is going to produce a couple of problems -1- hearing damage & 2-concentration problems which we don"t need in aviation.My approach to this would be to look around for a very comfortable acoustically inert helmet. 2 options- find one that fits the bill amongst your mates (or this forum) and purchase one of those or go the motorcycle helmet approach and fit your own electrics. Because we all have different head shapes and sizes it"s a very personal purchase to get a good helmet so you really need to try them. (you"re going to raise a few eyebrows when you ask to take their new helmet outside and listen to the exhaust note of a harley 2 inches from the end of the pipe!)Now that will take care of the earphone or reception side of things we still have the problem of the microphone placement, baffling and circuitry. The next main hurdle is that in the front of the helmet is a nice clean clear plastic sheet (the visor)which is also a good medium for letting in the outside wind and engine noise. That microphone needs to be mechanically isolated from the helmet (to stop the noise being transmitted into the microphone housing mechanically) and there are really only 2 ways to do that - with foam - the really light stuff or a microphone boom. It now depends on how much room you have inside the helmet. After doing all of this there will probably STILL be some noise coming in through under your chin and neck area. There are commercial helmets now incorporating a neoprene sheet attached to the front visor which goes some way to helping.And your last avenue of correction is noise cancelling. There are 2 methods here - the first is mechanical. This is where the microphone has an inlet in the front and back of the diaphragm (that"s the bit in the mic that collects the sound vibrations and converts them to electric pulses)The principle behind this is the external sound hits both sides of the diaphragm simultaneously and cancels out, however since the pilot is only talking into it from one direction, only one side is exposed to the vibrations and they get converted into the electric pulses that we need. In a previous post in this thread I described having to blank off the outside pickup to correct a noise problem which would seem to be coming from the visor but not reflecting back off the pilots face to give the equal sound level on both sides of the diaphragm to cause the wanted noise cancellation. The last noise cancellation tool is electronic- and there are 2 methods we can utilize here. The first is to use 2 microphones and in the same way as the noise cancelling microphone we collect the signals from both mics and electronically just allow through the sounds that come from one of the mics. For example one would be outside the helmet the other inside - a bit cumbersome in the environment that we operate in. The second method is to filter the sounds and this is the method used commonly in our helmets. How it works is the electronic filter removes the sounds above and below certain frequencies concentrating on allowing only the frequencies used in human speech to pass through. There are other tricks but I won"t go into them here.Bones I"m sorry that I couldn"t give you a model number, price and where to get it but as you can see there is a lot to them.

[Gleeso]

Thanks for that Bones.Matt

[bones]

Chook , the hearing thing was why i was asking, i knew it wasnt good.However early testing(3 min lap around hangar) of the helmet i got now proving to be very good, comfortable, QUIET, and the best bit my bestest mate

[GraemeMonro]

Chook , the hearing thing was why i was asking, i knew it wasnt good.However early testing(3 min lap around hangar) of the helmet i got now proving to be very good, comfortable, QUIET, and the best bit my bestest mate