Microphone Quality

Quality of the microphone can have a dramatic impact on speech recognition. A microphone that is sensitive enough to detect the entire range and frequency of a human voice is equally likely to detect many background noises in the environment. Background noise and microphone hiss can pose serious problems to voice recognition software. To be effective for voice and speech recognition, a microphone must be both highly directional and sensitive.

You should use a digital microphone. Most microphones that come with the speech recognition software packages are analog and are often included as "free" items. These "free" microphones should not be used for serious speech recognition users.

Some analog microphones can reject ambient (background) noise. While most speech recognition software has built in keyboard toggles to turn the microphone off, you may want a microphone with an on/off switch.

Microphone Placement

The placement of the microphone can impact performance. Avoid placing the microphone directly in front of your mouth since the letter "p" often results in a blast of air directed forward. If possible, place the microphone slightly to one side of your mouth. This should also help in reducing nasal sounds from being received by the microphone.

If you are using a desktop microphone, be careful where you position the base of the microphone as it may pick up sounds from the keyboard. If you have a CRT monitor and a desktop microphone, you may want to consider mounting the microphone off of the top or on the side of the monitor. LCD monitors tend to have too small of a body to effectively mount the microphone.

As you speak, the microphone is picking up the sounds from your voice as well as background sounds from the room in which you are speaking. Therefore it is desireable to have a high sound/noise ratio. The close the microphone is to your mouth, the higher the ratio of sound to background noise.

The noisier the room is, the closer the microphone must be placed to the talker to provide sufficient sound/noise ratio for good voice recognition.

Types of Microphones

Unidirectional Condenser Microphones / Desktop Microphones

Unidirectional microphones are sensitive to sounds from only one direction. These microphones provide uniform and smooth sound reproduction over a wide audio range. They exhibit a sensitivity for sound originating in front and rejection of undesired sounds at the back of the microphone.

Can be mounted to the desk or monitor in the form of a Boom or Gooseneck. Microphones that utilize the bias power from the sound card do not need an external or battery power supply which is an advantage if you are trying to use one with an older model laptop.
Is typically a condenser microphone requiring an external DC power source. The sound quality is lower.
.Audio 15 PC Microphone (http://www.plantronics.com/north_america/en_US/products/cat640035/cat1200101/prod5020012)
from Plantronics

Headset Microphones

Wearing the microphone on your head (headset) will keep the microphone at a precise distance from your mouth and will result in a more consistent recording of your voice.
If not a wireless headset, you are somewhat limited by the wires that connect the headset to the computer.
CS50-USB Wireless Office Headset System (http://www.plantronics.com/north_america/en_US/products/cat640035/cat5480033/prod5300004)
The CS50-USB from Plantronics extends wireless freedom to your softphone. It’s the first wireless headset for VoIP applications with remote call detection and answer/end capability via PerSonoCall™ .software.

NC-7100 USB Headset (http://www.andreaelectronics.com/Buy/ProductDesc/NC7100.htm)
from Andrea Electronics

USB Microphones

These are digital microphones that convert your speech into digitized audio without the use of a sound-card.
Does require use of systems that have available USB ports.
DSP-500 PC Headset (http://www.plantronics.com/north_america/en_US/products/cat640035/cat1430032/prod440044)
Plantronics DSP-500 digitally-enhanced gaming/multimedia headset with full-range stereo sound. It's perfect for multimedia applications such as games, CD's and MP3 music, speech recognition and voice applications.

Handheld Microphones

For use in environment in which use of a wireless headset is prohibited yet there is still a need for a portable microphone. These microphones often have additional buttons for specific dictation and recording functions.
Must be carried. Features may be limited to those offered by the manufacturer (i.e., these microphones might not be as portable as USB or Unidirectional microphones). Some handheld microphones are omni-directional which allows for the recording of sounds from any direction and would result in more background sounds being heard during speech recognition.
ANC-300 Dual Function Hand-Held Computer Microphone (http://www.andreaelectronics.com/Buy/ProductDesc/ANC300.htm)
from Andrea Electronics

Desktop Directional Array Microphones

Using more than one microphone, the Directional Array Microphones combine inputs from several sources to more accurately separate the speech from ambient noises. By analyzing the audio streams from each microphone it is possible to determine the location of sound sources which results in a more "unidirectional" microphone. This type of signal processing is what occurrs in regularly in people. The two ears on each side of your head receive slightly different audio signals (each is facing the opposite direction). The differences between these signals are analyzed by your brain (in a type of triangulation) to enable you to determine the location of the source of the sound.

Speaker is unteathered and does not need to wear a wireless device.
Cost and required system resources are greater due to the additional signal processing that takes place. The user is limited to the locations where the directional array is sensitive (usually directly in front of the array).
Stereo USB Audio Adapter & Superbeam Array Microphone Bundle (http://www.andreaelectronics.com/Buy/ProductDesc/superbeam_mic_bundle.htm)
from Andrea Electronics

Other Vendors

eMicrophones (http://www.emicrophones.com/index.asp)
Computer Microphones for Voice or Speech Recognition

SpeechControl.com (http://www.speechcontrol.com/index.asp)
Our Web Site provides microphones and headsets for computer and call center needs.

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