BlackBerry Forums Support Community - View Single Post

Hitek146 · 02-10-2007, 02:10 AM

There were extensive tests done years ago to see if the RF from standard cell phones does any damage to organic tissue(your brain), and they couldn't find any link to cancer, or anything. It was on a documentary or something...

The sound that you are hearing is voice coil of the speaker being energized by the electromagnetic field produced by the cell phones radio transmitter. A speaker voice coil is technically an "inductor", which is often used in circuitry for it's magnetic and resonant properties. This makes it an excellent "antenna", and a speaker's voice coil design is almost identical to that of the antenna used on standard metal detectors(aka treasure finders). Couple their RF sensitivity with the fact that the speakers cone structure will highly amplify any voice coil resonation in the audible frequency range, and you have yourself a very efficient RF receiver/amplifier, although of admittedly useless bandwidth. Almost any speaker is capable of this, although shielded speakers will block most of this. Most speakers aren't well shielded, though, and this includes some very high-end speaker with cabinets made only of wood. While the actual drivers, themselves, inside the cabinet may have some built-in shielding, the increased efficiency of the more expensive driver will make them that much more sensitive in the first place. Couple that with the fact that the larger driver size(likely the woofer or subwoofer) in a typical home tower enclosure amplify whatever is picked up by the voice coil even more than a small speaker, and you could see how it might be quite loud also...

All of this with no active amplification... Cool, huh???

Edit: Forgot to say that, as partially mentioned before, the amount of interference can depend greatly on the frequency range that the phone is operating in, and this can depend on what carrier's SIM is installed in the multi-band phone. Since lower frequencies inherently travel further over a given distance with less loss than a higher frequency, Nextel's iDEN network has been one of the worst, operating in the 800-900MHz range...

02-10-2007, 02:10 AM	#37
Hitek146 New Member Join Date: Feb 2007 Model: 7280 Posts: 10	There were extensive tests done years ago to see if the RF from standard cell phones does any damage to organic tissue(your brain), and they couldn't find any link to cancer, or anything. It was on a documentary or something... The sound that you are hearing is voice coil of the speaker being energized by the electromagnetic field produced by the cell phones radio transmitter. A speaker voice coil is technically an "inductor", which is often used in circuitry for it's magnetic and resonant properties. This makes it an excellent "antenna", and a speaker's voice coil design is almost identical to that of the antenna used on standard metal detectors(aka treasure finders). Couple their RF sensitivity with the fact that the speakers cone structure will highly amplify any voice coil resonation in the audible frequency range, and you have yourself a very efficient RF receiver/amplifier, although of admittedly useless bandwidth. Almost any speaker is capable of this, although shielded speakers will block most of this. Most speakers aren't well shielded, though, and this includes some very high-end speaker with cabinets made only of wood. While the actual drivers, themselves, inside the cabinet may have some built-in shielding, the increased efficiency of the more expensive driver will make them that much more sensitive in the first place. Couple that with the fact that the larger driver size(likely the woofer or subwoofer) in a typical home tower enclosure amplify whatever is picked up by the voice coil even more than a small speaker, and you could see how it might be quite loud also... All of this with no active amplification... Cool, huh??? Edit: Forgot to say that, as partially mentioned before, the amount of interference can depend greatly on the frequency range that the phone is operating in, and this can depend on what carrier's SIM is installed in the multi-band phone. Since lower frequencies inherently travel further over a given distance with less loss than a higher frequency, Nextel's iDEN network has been one of the worst, operating in the 800-900MHz range... Last edited by Hitek146; 02-10-2007 at 02:29 AM..
Offline