Sound and Hearing?

Two identical loudspeakers are located at points A and B, 2.00m apart. The loudspeakers are driven by the same amplifier and produce sound waves with a frequency of 784Hz. Take the speed of sound in air to be 344m/s. A small microphone is moved out from point B along a line perpendicular to the line connecting A and B.

If the frequency is made low enough, there will be no positions along the line BC at which destructive interference occurs. How low must the frequency be for this to be the case?

both waves must be counter-phased at a given point. This could be attained when 2m/lamvda = integer N, but at 784Hz lambda = 344/784 =0.44m and N=2/0.44 =4.55; now if N=4 then lamvda =2m/N = 2/4 =0.5m, hence v=c/lamvda = 344/0.5 = 688Hz;

Peltor 97044 Tactical 6S Active Volume Hearing Protector $52.99 The Peltor tactical 6S hearing protector muff blends comfort, performance, and protection with electronics that limit amplified sounds to 82 dBA within 5 milliseconds. An active-volume system provides distortion-free amplification of low-level sounds up to 19 dBA. The folding design includes independent volume controls in each cup….

Detect Ear Professional Listening Device – DET EAR by KJB $389.99 Listen to sounds up to 300 yards away with the pinpoint accuracy of the Detect Ear. The Detect Ear provides high performance with the most advanced audio circuitry and a 20″ snap together parabolic dish….

Sounds Amplifier $9.99 Listen to everything loud and clear with this hearing enhancer! Hear sounds from over 65ft. away. Amplifies sound up to 50 dB. Perfect for hunting, watching TV and conversations. Lightweight, compact unit fits into shirt pocket or clips on belt….

The Stealth Secret Sound Amplifier $27.98 Designed to look like an expensive cell phone earpiece, the Stealth S.S.A. works as a sound enhancer so you can enjoy conversations and even hear soft voices from 50 feet away. It is lightweight and compact, so you won´t even feel like you´re wearing it. The Stealth SSA has a soft foam handle that fits snuggly over the ear and directional amplification to help you hear what you have …

MDHearingAid Acoustitone PRO Hearing Aid Have you ever wondered why hearing aids cost so much more than digital cameras, DVD players, and televisions? The MDHearingAid Acoustitone PRO hearing aid was designed by an Ear, Nose & Throat doctor to help the millions of people with hearing loss that cannot afford traditional hearing aids. Built to exact specifications, using world class components, the MDHearingAid Acoustitone PRO provides sou…

Turbo EarTM $28.03 Turbo Ear&#153 uses advanced microprocessor technology to deliver crystal clear reception while reducing background noise. Features volume and on/off controls. Includes three silicone tips, storage case and AC adapter. Rechargeable-each charge lasts up to seven hours. Perfect to use at home, movies, church, restaurants and more. Imported….

Ear Force X11 Amplified Stereo Headset with Chat $59.99 Voyetra Turtle Beach Ear Force X11 Headset – Stereo TBS-2155 Headsets & Earsets…

Plantronics H251N SupraPlus NC Headset $59.99 Single earpiece headband. Adjustable headband. Wideband frequency response for better audio quality. Quick Disconnect. Requires M-12, MX-10, CS-10 or CA-10 modular amplifier/adapter. Wired: Telecom: Office Headsets…

Plantronics HW261N Binaural Headset $69.00 Adjustable headband. Wideband frequency response for better audio quality. Quick Disconnect. Requires M-12, MX-10, CS-10 or CA-10 modular amplifier/adapter . Wired: Telecom: Office Headsets…

Sonic Super Ear Personal Sound Amplifier $29.95 Buy the Sonic Super Ear from ActiveForever to improve your listening experience. ActiveForever found the Sonic Super Ear which is like binoculars for your ears. Whether you are experiencing mild to moderate hear loss, or simply want to have the ability to hear the sounds around you more clearly, the Sonic Super Ear will improve your listening experience. For entertainment, professional, or necessi…