You're walking down a busy street when your cell phone rings. Do you pick up and shout over the din while straining to listen to your caller, or do you miss the call? If you have a noise-canceling headset, you don't have to choose. It's designed to eliminate environmental noise so you can have a conversation at a normal voice level almost anywhere. The mouthpiece of the noise-canceling headset works by detecting only your voice vibrations, which the device picks up through your jaw bone.
Noise-canceling headsets help out in many environments. You can use it in the office when you're trying to conduct a business call as your co-workers gab away near your desk. It's a discreet option when you're on a busy street and don't want to shout your credit-card number into your cell phone. Now that several states are requiring hands-free cell phones for drivers, headsets also provide a perfect alternative to breaking the law.
But how does your phone know which voice to pick up? In this article, we'll look at how noise-canceling headsets work.
Noise-canceling Headset Technology
How does the headset know which noise is your voice and what noise to cancel? To answer that, try this: Plug your ears with your fingers so that you can't hear the noise around you. Now talk. You can still hear yourself, right? Your voice sounds different from the way it sounds when your ears are unblocked, but you can definitely have a conversation with yourself in your head. Whether that's a good or bad thing is up to you.
How is this possible? Thank your jaw bone. When you speak, you create vibrations that travel through the ear and reach another person's ear. Regular phones use air conduction hearing, which uses the outer ear to catch sound waves. The sound waves are then transported through the middle and processed in the inner ear. Noise-canceling headsets combine this air technology with bone conduction hearing [source: Anjanappa et al]. The bone conduction method transmits sound vibrations directly to the inner ear along the bone itself. For more on hearing, see How Hearing Works.
The mouthpiece on a noise-canceling headset is actually two microphones -- one for air conduction and the other for bone conduction -- combined into one. This is called a bi-directional microphone. The microphone sends the signal to a sound processor. The processor then sends the signal across the airwaves so the person on the other end of the call hears your voice. This is similar to the process of voice transmission featured in hearing aids.
Because the sound hasn't passed through your entire mouth (since your lips also help with speech) when it hits the jaw, bone conduction is slightly lower in sound quality, so the air conduction method of transmission is needed to make your voice clear. The noise-canceling headset uses the bone conduction method only to discern the correct noise to recognize, thus filtering out surrounding noise. This active noise control can be controlled by an on/off switch on headsets [source: Aliph Jawbone].
Noise-canceling headsets help you hear yourself clearly despite the noise around you, but how do you hear who you're talking to? Read on to find out.
Noise-canceling Headset Parts
While the microphone is the most complicated part of a noise-canceling headset, there are other features to consider. The headset can either include a single earpiece, often with an ear hook for better stability, or a double earpiece similar to a set of headphones. The single earpiece allows a caller to be aware of what's going on outside the call -- most helpful when you're walking down a busy street. However, the double earpiece allows you to hear a call more clearly, which may be desired in an office setting.
Headset design has come a long way since its invention in 1910 [source: Utah History to Go]. Noise-canceling Bluetooth headsets are available for a variety of models. Sizes continue to shrink and adapt to the changing design needs of the consumer. The Jawbone Bluetooth-enabled headset, for example, is designed to look more like a hair accessory than a phone [source: Aliph Jawbone]. Similarly, the Plantronics Discovery 925 features a diamond-shaped earpiece that looks more like jewelry than a headset [source: Plantronics].
The earpieces in noise-canceling headsets work by sealing off your ear from outside noises. Noise-canceling headsets come with earpieces in a variety of sizes so that anyone can get a perfect ear seal. For more on how noise-canceling works in the earpiece, see How Noise-Canceling Headphones Work.
Most headsets have connectors and adapters, or they can be synced with your Bluetooth-enabled phone. Check with the manufacturer to ensure your phone will work with your headset.
The controls on a headset are typically minimal, since you would use it in conjunction with your regular phone. The controls are typically limited to a "talk" button and an on/off switch for the noise-canceling feature. The noise-canceling feature uses a little extra power, so some users can choose not to use it in every situation.
For more information on noise-canceling headsets, please see the links on the next page.
Related HowStuffWorks Articles
More Great Links
- Aliph Jawbone. (6/11/2008) http://www.jawbone.com
- The Boom. (6/9/2008)http://www.theboom.com
- "Ety-Com Hands-Free Noise Isolating Headset." The Travel Insider. (6/9/2008)http://www.thetravelinsider.info/roadwarriorcontent/etycomheadset.htm
- Etymotic. (6/9/2008) http://www.etymotic.com/pdf/etycom-manual.pdf
- Huang, Xuedong D., Liu, Zicheng, Zhang, Zhengyou, Sinclair, Michael J., Acero, Alejandro. Free Patents Online. "Multi-sensory speech detection system." Free Patents Online. (6/11/2008) http://www.freepatentsonline.com
- Lee, Nicole. "Aliph Jawbone 2 (silver)" CNET reviews. (6/5/2008)http://reviews.cnet.com/headsets/aliph-jawbone-2/1995-13831_7-33018086.html?tag=cnetfd.mt
- Mossberg, Walter S. "Cellphone Headsets With Less Bulk, Background Noise." The Wall Street Journal. May 15, 2008. (6/9/2008)http://ptech.allthingsd.com/?p=222
- Patent Storm. (6/11/2008) http://www.patentstorm.us/patents/7269266/description.html
- Plantronics. (6/11/2008)http://www.plantronics.com
- Roberts, Mary Rose. "Hear comes the show." Mobile Radio Technology. 01 Mar 2008.
- Utah History to Go. http://historytogo.utah.gov/salt_lake_tribune/history_matters/070801.html
- U.S. Hands Free Laws. (6/13/2008)http://www.drivinglaws.org/
- U.S. Patent Database, US Patent 7269266. (6/13/2008) http://www.uspto.gov/patft/
- Zheng Y. et al., "Air and Bone-Conductive Integrated Microphones for Robust Speech Detection and Enhancement" Automatic Speech Recognition and Understanding 2003.