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Q & A: Blackberry and Bluetooth Interference

We've been experiencing Blackberry and Bluetooth interference with our wired microphones. The interference consistently occurs, regardless of where the devices are located in the room or how close they are to the microphones. Would adding shielding to our mics/cables help?

Q: We've been experiencing Blackberry and Bluetooth interference with our wired microphones. The interference consistently occurs, regardless of where the devices are located in the room or how close they are to the microphones. Would adding shielding to our mics/cables help?

— Joe Grandalski, digital media specialist/audio engineer, Alexander Gallo & Associates Court Reporting and Video Services Inc., Atlanta

A. Adding shielding will help, but it might not be enough. These problems typically occur with devices that use a GSM network. Unshielded system devices such as computer speakers present the biggest problems. The sound is usually audible as a “dit, dit, dit, dit,” type of sound, which isn't predictable. The microphones —usually condenser mics — should be connected with shielded cables with proper terminations. Installing the cabling in conduit for additional shielding will also help to bring down interference. Several manufacturers now have microphone products with RF filters. A system designer should consider using those microphones when they anticipate heavy use of cellular devices in the space.

— Matthew J. Moore, principal consultant, Cavanaugh Tocci, Sudbury, MA

Next Month's Question: We're designing a multipurpose auditorium that will also be used for film presentations. Our client wants to have surround sound from a DVD player at the stage and in the control booth 100 feet away, but the budget will only allow for one digital processor. Which digital audio format — AES-EBU, AES-3ID, SPDIF (either optical or over an RCA cable), TOSLINK, etc. — would work best for sending the signal over that distance?

Send your responses to proav@ascendmedia.com. If you have a question you'd like your AV colleagues to answer, send it to the same email account. If we use your question, we'll send you a coolPro AVgift.



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