[Jason Raath]

Jason Raath  asked the Naked Scientists:
   
Hi Chris,
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When my cellphone rings next to a speaker (TV, radio, pc etc), I get that terrible buzzing noise that comes through, as I'm sure everyone else does. Does this noise occur when people who use hearing aids use cellphones and if not why? Also, why would the cellphone speaker itself or hands free kits not get that buzzing noise when all others do?
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Thanks, love your show on Fridays on 702, and try never to miss it.
 Â 
Cheers,
 Â   
Jason Raath

What do you think?

[lyner]

I haven't heard it on mine. I just tried it again as a test. No effect. Just as well, really!

[LeeE]

When a call is made to a cell phone there is two-way communication between the phone, as the phone needs to tell the base-station when and whether the call is to be connected.  The radiation from the cell phone as it's negotiating this stuff shouldn't affect loudspeakers directly as they're handling much more power and at voltages and currents that would swamp anything put out by a cell phone.

The low-voltage electronics in radio and TV tuners, and even the pre-amp stages of the amplifier that drives the loudspeakers can be susceptible to cell phone radiation though: I've certainly heard it on my portable radio, but only when the phone and radio have been orientated in a certain way.

The electronics found in hearing aids and hands-free kits can be shielded against this radiation, or may be designed to operate at such frequencies such that the phone signals can't induce a significant level of harmonics.

[lyner]

Hearing aids have a huge advantage in that they are very small (at least the modern ones). Being so small, they are comparatively poor as receiving antennae - even for the  high frequencies used for GSM.  But their digital signal processing chips must work at a high frequency with a very low voltage supply, making interference an issue in their design, I'm sure.
Pretty much everything else with an amplifier in it seems to be susceptible when you hold the phone right next to it. (Even when equipment is only on standby!)

[techmind]

When my cellphone rings next to a speaker (TV, radio, pc etc), I get that terrible buzzing noise that comes through...
Does this noise occur when people who use hearing aids use cellphones and if not why?

I had a hearing aid which is over ten years old, a small NHS analog aid which is absolutely awful for mobile phone interference. Any use of a mobile phone within a 1 metre radius of that causes very loud buzzing.

My newer Siemens (also NHS) digital aids only suffer a very very faint buzzing when you put the phone right up against them - but not bad enough to be a real problem. I tend to remove my hearing-aids to use the phone anyway, although it is a bit of a pain.


Basically the mobile phone signal can get into any part of an audio circuit, but the effect will be most significant if it gets in where the audio signal is weakest, and subject to the most amplification - i.e. at the microphone. The microphones used in mobile phones, and probably in modern hearing aids have a small capacitor soldered on the back of them (or even inside) which does not affect the wanted audio signal but effectively presents a short-circuit to radiowave/microwave energy of mobile phones and other transmitters. Careful design of the printed circuit board, keeping sensitive traces short and sheilded all help to minimise interference problems.

[syhprum]

I am somewhat deaf and would like a hearing aid of some sort but not at the prices quoted, I can buy a mobile phone handset a much more complex device than a hearing aid for about 1/30 of the price quoted for the hearing aid.
What I would like is a mobile phone which would output its microphone to an earphone but no one seems to make them.

See this URL for the ludicrous prices

http://www.halfpricehearing.co.uk/

[RD]

What I would like is a mobile phone which would output its microphone to an earphone but no one seems to make them.

Some mobile phones permit a wireless "Bluetooth" earphone.
 
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http://en.wikipedia.org/wiki/Bluetooth#Bluetooth_profiles

[lyner]

I am somewhat deaf and would like a hearing aid of some sort but not at the prices quoted, I can buy a mobile phone handset a much more complex device than a hearing aid for about 1/30 of the price quoted for the hearing aid.
What I would like is a mobile phone which would output its microphone to an earphone but no one seems to make them.

See this URL for the ludicrous prices

http://www.halfpricehearing.co.uk/

If you are in the UK, go to your GP. I did and got two hi tech aids for free from my local audiology department- (that 'rubbish' NHS again).

[techmind]

I am somewhat deaf and would like a hearing aid of some sort but not at the prices quoted...

If you are in the UK, go to your GP. I did and got two hi tech aids for free from my local audiology department- (that 'rubbish' NHS again).

Hear hear! They'll even supply you with an ongoing supply of free batteries (although the tiny battery will probably last 2-3 weeks if you only use the aids for 12 hours/day or somesuch).

It might take a while (weeks/months) to get the appointments, but the sooner you join the queue the sooner you'll be seen.

[lyner]

We have a 'drop in' repair and replacement centre at the Royal Sussex County Hosp. and they are nothing short of magic. You may need to wait an hour but, what the hell. it's free and they're so helpful.
Shame the free batteries are no good for torches and radios. []