Choosing the Best Headset Microphone

A quality noise canceling headset is needed to realize the full potential of today's speech recognition software in an office or warehouse environment. The best of these headsets are gradient microphones of order one - a technology which dates to the velocity microphones of the 1930s. The physics of gradient microphones were described by Harry F. Olsen in 1946.

Headset makers have approached the theoretical ideal of a gradient microphone with varying degrees of success. A gradient microphone may be implemented in one of two ways: a single bi-directional microphone element, or two identical omni-directional microphone elements of opposite phase. Both pose practical constraints which determine to what degree noise is canceled in the voice bandwidth.

"A gradient microphone of order one may be made up of two oppositely phased units," according to Olsen. Olsen prescribed two elements to achieve the maximum noise canceling bandwidth allowed by the microphones available in 1945.

Advances in microphone technology have allowed the development of a single element gradient microphone. The noise canceling performance of a single element gradient microphone is determined by its success in matching the acoustic impedance to either side of the microphone diaphragm and the spacing of the two sound ports.

Active Noise Cancellation

The use of two out of phase microphone elements to comprise a gradient microphone is not new. Subtraction of signals from two omni directional microphone elements has been in the public domain since 1946.

No two microphones are identical in sensitivity or frequency response. A manufacturer of a two element gradient headset microphone must normalize the sensitivity of the two elements at a single frequency - preferably midway through the audio band.

To the extent which the microphone sensitivities are mismatched at a particular frequency, noise is not canceled. Manufacturing variations of individual microphone elements cause wide variations in the noise canceling performance of two element gradient microphones.

A single element gradient microphone draws power for a single transistor. A dual element gradient microphone draws power for three transistors. Many sound cards limit how much current may be drawn through the microphone jack. Choosing a dual microphone element headset multiplies the likelihood that the user will require a separate battery adapter to provide sufficient power for the headset.

Here are some measures you should consider when deciding which headset microphone will serve you best:

On Axis Performance

On axis performance charts display how well the headset microphone cancels noise on its sensitive axes: 0 to 180 degrees. For an ideal gradient microphone, the far field response for 0 and 180 degrees would be identical.

Reverberant/Polar Cancellation

On a polar chart, an ideal gradient microphone would exhibit a bi-directional polar pattern at all frequencies. A polar chart is a two dimensional representation of how well a gradient microphone cancels reverberant noise in three dimensions.

Microphone Noise

When there is no audio input to a microphone, some residual electrical output noise still exists. This output results from several electrical and acoustic factors, but is primarily due to the quality of the impedance conversion transistors used.

The relative magnitude of the acoustic input to the electrical noise output may be thought of as "signal to noise" and may be expressed in terms of the equivalent noise sound pressure (ENP) is a close estimate of the perceived magnitude of the microphone noise, were it to appear as audio noise at the input of a perfectly quiet microphone.

Current Drain

Current drain is a measure of how much current the headset microphone draws from the sound card jack. Many sound cards are able to source only a limited amount of current. When this happens, the user must troubleshoot the problem and purchase a battery adapter at extra expense and inconvenience.

Tips for Users

If you have purchased a microphone that measures up according to the above criteria, but you are still finding the computer is not recognizing dictation like you would want it to, it may be a matter of position and power.

First, check the position of the boom microphone. It is essential that the microphone is in the optimum position. The correct position is approximately 10mm from the tip of the boom microphone to the side of your mouth. Positioning the microphone correctly will enhance your dictation significantly.

Another suggestion is to use a battery adapter. If you are experiencing low levels of response from your microphone, a battery adapter will give you the boost you need.

Timothy Wickstrom is the engineering manager at Emkay Innovative Products, 2800 West Golf Road 1151 Maplewood Drive, Itasca, Ill. 60008. This article was adapted from his paper "Gradient Headset Microphones: Headsets and Performance," which can be attained from Emkay by calling Teresa Bosch at 847-952-3964.

Andrea Introduces Far Field Microphone

Andrea Electronics Corp. announced at the recent PC Expo, the introduction of its Digital Super Direction Array (DSDA) microphone technology, which allows for the cancellation of background noise and transmission of a clear voice signal even when the speaker is at a distance from the microphone.

Such technology is needed for emerging applications in the areas of automobile PCs, desktop speech recognition, hand held devices, audio/video and "whiteboard" teleconferencing, office and home automation systems, car phones, camcorders and hearing aids.

DSDA technology incorporates an array of microphones to eliminate unwanted noise while providing a natural language, human/machine interface capable of producing a wide range of high performance audio and acoustic voice solutions.

"Today, more than ever, people are using speech recognition, network communications and other voice-enabled natural-language applications as a means to enhance the way we communicate," said Douglas J. Andrea, co-president of Andrea Electronics Corporation.

Andrea said the new microphone technology has the ability to focus on a particular source, and eliminate ambient noise, which causes distortion and interference from computing applications. He compared the DSDA microphone to a camcorder, which can zoom in and out on an intended subject.

The DSDA microphone technology will be demonstrated in numerous voice applications, including:

  • Automobile PCs - DSDA's ability to conquer extraneous noise (traffic, etc.) will allow automobile PCs to receive clear voice commands.
  • Speech recognition - voice clarity for desktop speech recognition environments is significantly enhanced with DSDA.
  • Videoconferencing - DSDA provides enhanced performance for videoconferencing and similar communications technologies.
  • Home Automation Systems - dramatic improvements to the quality of audio communications provides a hands free solution for use in a smart home.

    For more information contact Andrea at www.andreaelectronics.com.

    Adapter from GN Netcom

    GN Netcom/Unex recently announced the availability of the GN Netcom PC / Headset Adapter, which allows hands-free access while utilizing the power of computer telephone integration. The GN Netcom PC / Headset Adapter directly connects any GN Netcom headset to a PC sound card, enabling the user to take full advantage of the computer's audio capabilities, including voice annotation and voice recognition.

    "The GN Netcom PC / Headset Adapter is an ideal headset solution for the emerging small office/home office market, as well as for professional call center moving into computer telephony," said Roland Nutter, product manager at GN Netcom/Unex, Inc. "The Adapter provides users of PC sound card applications with the same hands-free capability experienced by traditional telephone headset users."

    The Optima-G is the lightest professional grade headset available, and features an ergondynamically contoured speaker which reflects the shape of a human ear, a noise canceling microphone, a strong Duraflex boom, Pure Sound, AccuBass speakers and a Stay Put ratcheting headband for all-day comfort.

    GN Netcom/Unex designs and manfacturers high quality telephone headsets and accessories in the telecommunications industry. Headquarters and manufacturing are based in Nashua, N.H.

    For more information, contact GN Netcom/Unex at 800 826-4656

    VXI Introduces Parrot Translator, Switch

    VXI Corporation recently introduced the Parrott™ Translator and Parrott Switch 60V designed to work in conjunction with Parrott brand headsets to address and solve voice recognition performance issues that often occur due to hardware incompatibility.

    Both products enable users to perform multi-tasked headset functions with greater sound quality, comfort and convenience.

    The Parrott Translator makes Parrott headsets the first to be universally compatible with any PC, soundcard or laptop to ensure successful voice recognition. Attached to the headset cord and ready to use "right out of the box," the Parrott Translator is able to detect and properly balance microphone bias voltage and resistance.

    The Parrott Translator adjusts for a constant output level in voice band, and eliminates variation between microphones.

    The Parrott Switch 60V is a computer-telephony integration device that has the benefit of enabling the user to seamlessly alternate between a PC and the standard telephone. By changing the microphone path at the push of a button, the Parrott Switch 60V provides users with the convenience of a single headset for a multitude of tasks. It lets users maintain contact with a caller while inputting data into a computer.

    The Parrott Switch 60V is intended for call centers, help desks and other computer-telephone integration applications. These applications often have the problem of what to do about the confusing, constant switching between the headset connected to the PC and the headset connected to the customer. Without this device, the user must switch headsets, continually unplug and re-plug separate cords, and risk tangled wires and upset customers. By redirecting the microphone path at the push of a button, the Parrott Switch 60V offers users the convenience of a single headset capable of handling many tasks.

    "The success of given a voice recognition software program hinges on the headset's technical precision - ensuring that the human voice is being repeated and understood by the software," said Victor Temple, executive vice-president of VXI.

    "Parrott headset systems repeat exactly what the user says to the software and make certain the spoken word appears on the screen."

    One of the keys to this accurate voice recognition performance is the Parrott headset's sensitive microphone, which has been engineered to maintain consistent output at all times and under all conditions. The microphone's design, circuitry and housing also combine to eliminate background noise and minimize distortion.

    VXI believes the Translator and Switch can work in conjunction with Parrott headsets to further enhance voice recognition performance and ease of use.

    In the recent past, problems of voice recognition failure and unnecessary customer returns resulted from incompatibility between headsets and hardware. VXI believes it has solved these problems and others with their Translator, which is attached to the headset cord and ready to use "right out of the box."

    For more information, contact VXI Corporation, One Front Street, Box 490, Rollinsford, NH 03869, call: 800-742-8588 or visit VXI on the world wide web at http://www.vxicorp.com.

    Telex Enables Speech at AutoPC debut

    Telex Communications Inc.'s Computer Audio Group recently helped Microsoft solve a unique audio problem. When Microsoft announced their Auto PC, which uses speech technology, at the CES show in January, Telex provided noise canceling headsets, interface technology and speech recognition testing to deliver a complete solution.

    The Auto PC, powered by Windows CE 2.0, provides connectivity, information on demand, and enhanced entertainment to the automobile via interactive speech technology. The system allows for the use of speech recognition through the speech-technology user interface, enabling oral commands and using speech synthesis to communicate information.

    For CES's many attendees, who generated a great deal of ambient noise, Microsoft demonstrated AutoPC at their booth with Telex headsets.

    For more information, contact Deborah Haupert, Telex Communications, Inc. 9600 Aldrich Ave., South, Minneapolis, MN 55420-4288, or on the web at http://www.computeraudio.telex.com.

    Labtec Offers New Line, Adds FlexNeck Microphone

    Labtec recently announced ClearVoice™, a new line of advanced PC speech recognition headsets and microphones.

    ClearVoice features three models specifically designed to meet the technical demands of speech recognition. The ClearVoice microphones feature NCAT2 (Noise Canceling and Amplification Technology, Version 2) a Labtec proprietary microphone technology that optimizes the performance of PC speech recognition and other voice-enabled software applications.

    The NCAT2 microphone element delivers speech output in noisy environments, and are designed to be compatible with virtually all sound cards. ClearVoice models will be available to consumers in September.

    The new Labtec ClearVoice microphones with NCAT2 technology will help our customers get the best results from their PC speech recognition software," said Darrell West, director of marketing for Labtec.

    The three new ClearVoice PC speech recognition models are:

  • LVA-7330 Clear Voice Head Microphone - A head-mounted microphone designed for applications that do not require audio feedback, this microphone is a lightweight alternative to a conventional headphone/microphone combination and will have an estimated retail price of $29.95.

  • LVA-8450 ClearVoice Mono Headset/Boom Microphone - A headset microphone combination featuring a headphone volume control and microphone mute switch, this product is expected to retail at $39.95.

  • LVA-8550 Clear Voice Stereo Headset Microphone - A top-of-the-line headset and boom microphone system featuring a stereo headset, headphone volume control and microphone mute switch, this microphone will also retail at $39.95.

    Labtec also recently announced the addition of the AM-252 FlexNeck™ microphone to its full line of PC Voice Access™ microphones, headphones and headsets.

    The AM-252 is designed for multimedia applications, Internet communications and interactive audio uses. The line is widely available at retailers such as CompUSA, Computer City, Wal-Mart, Circuit City, Sears, Staples and Office Depot.

    The AM-252 is engineered with Noise Discrimination and Amplification Technology (NDAT), a Labtec proprietary technology that optimizes voice input accuracy for improved performance of Internet communications, multimedia and interactive audio applications. NDAT technology filters out background noise and enhances sound wave frequencies associated with speech, resulting in a clearer, more consistent signal and improved speed and intelligibility.

    "The AM-252, with its NDAT noise reduction capabilities, offers consumers a high-quality microphone for their PC voice access and multimedia applications at a very reasonable price point," said Darrell West, Labtec Director of Marketing for Labtec. "This new microphone model helps us expand our product line and continue to be the first choice of retailers and consumers for PC voice access and audio products," he added.

    The AM-252 is the latest addition to a full line of PC voice access, voice recognition and multimedia audio products. Labtec reports that its microphones and headsets are engineered to produce optimum voice audio signal clarity, which ensures that voice recognition software more accurately translates users' speech to text, and reduces the frequency of recognition errors.

    Labtec, which recently received full certification by Dragon Systems, currently manufactures 12 PC voice access models in a range of price points and performance levels, from entry-level to professional.

    For more information, contact Labtec, 14999 SE Tech Center, Place, Suite 350, Vancouver, WA 98683, call 360 896-2000 or visit the Labtec website at www.labtec.com.

    Lotus from Comfort

    Comfort Telecommunications has just introduced the new Comfort "Lotus." The Lotus is the latest addition to the Comfort Aries Line of award winning headsets.

    It is an over the ear headset, which comes standard with noise canceling microphone, flexible spring boom and an adjustable "Comfort fit" for a more secure and comfortable fit in your ear.

    This style is extremely light weight and comfortable and, according to Comfort, is preferred by people who concerned about their their hairdos.

    For more information, contact Comfort, 1407 SE 47th Terr. Cape Coral, FL 33904, or on the Internet at http://www.comfortel.com or call 800 399 3224.

    VCI Offers Wireless Headset System

    Voice Communication Interface Corp., recently announced the introduction of a new wireless headset system, the Universal VLC. This upgraded version of the VLC product line can function independently as a wireless microphone or headset, depending on the application.

    The Universal VLC has been successfully tested with all commercially available speech recognition systems. Users can "use the wireless microphone-only feature for a dictation application, or the wireless headset for two-way communication and audio feedback. The product provides a true hands-free and eyes-free solution to any speech application.

    Voice Communication Interface Corp. provides headsets for speech recognition, multimedia, and computer telephony applications.

    For more information, contact Voice Communication Interface Corp., at 203 393-3585 or visit their web site at www.vcivoice.com.

    New Headsets from Nortel

    Nortel Liberation recently announced the addition of three new headsets to its portfolio of call center products. All three are available in monaural and binaural wearing styles and feature a two year warranty from Nortel.

    The three headsets are:

  • The Performa features contoured sound-buffering enhanced receivers and ear-cushions for a better fit and a high-performance noise-canceling microphone.
  • The SupraXL features a click-stop adjustable headband for an ultrastable fit.
  • The Encore XL, a lightweight headset with tone control switching on the receivers for superior sound quality.

    For more information, contact Nortel at 1-800-4NORTEL of visit their web site at www.nortel.com

    Amplifier from AVID

    AVID Products recently announced the release of the MC1 Universal Multimeter Microphone Amplifier, designed to improve the quality of sound produced by computer sound cards.

    This unit can be used by almost any type of multimedia microphone to boost the output of the microphone to line level. The MC1 improves voice recognition functions by providing increased volume and enhanced clarity of sound.

    Users can simply plug a headset into the MC1 and then plug the MC1 into the computer.

    For more information, contact Frank T. Vollaro, president, Avid Products, Aquidneck Corporate Park, Middletown, RI 02842, or call 401 846-1300, or visit their web site at http://www.avidproducts.com

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