Microphone Usability (documented  with permission of Microsoft)

Microphones are necessary for speech recognition to function, and the quality/ergonomics of a microphone can make the different between an unusable speech product, and one where speech recognition shines. A good microphone will have half the speech-recognition error rate of a poor microphone.

However, microphones are one of the largest impediments to people using speech recognition. In general, the failure points are:

1. Users don't have a microphone.
2. Users don't have the microphone plugged into the computer.
3. The sound card isn't compatible with the microphone.
4. If the microphone gain is so high that clipping happens then accuracy will be terrible. If it's too low then accuracy won't be as good as possible.
5. Users don't know how to hold/position a microphone.
6. Cheap (poor quality) microphones are the norm. (Luckily, this is starting to change.)
7. The most accurate microphones require that the users wears them. Many users don't like wearing microphones.

If a speech aware application doesn't take all of these factors into account, many users will be unable to get speech recognition to function well. To avoid microphone problems, we recommend that your application use the Microphone Setup Wizard  

Usability of specific types of microphones

If you are considering bundling a microphone with your application, sound card, or PC, here is some usability information on specific types of microphones.

Close-talk

Benefits:

• Acceptable close-talk microphones now sell for about $50 (US) at computer stores, and are worth the expense if users wan't maximum accuracy.
• Highest accuracy of any type of microphone because the element is close to the mouth, and almost always near-field.
• Near-field element so it's noise resistant.
• User has his/her hands free.
• User can lean back in his/her chair and talk. (Make sure the microphone cord is long enough so users can lean back, even if their PC is under their desk.)

Problems:

• Most users dislike wearing something or being attached to their PC. Sometimes the cord gets tugged on when the user moves around.
• It's difficult to talk on the phone with a telephone handset while wearing the close-talk, unless the phone is routed through the headset. Some headsets have this functionality.
• Slow to put on and take off.
• The user has to reposition the element every time they put the microphone on. When the element position changes so does the sound of the audio. Users must be aware of this so they don't make this mistake.
• Sometimes users position the element directly in front of their mouth, causing recognition problems when they exhale onto the element. Users must be aware of this so they don't make this mistake.

Ear Piece

Benefits:

• Second only to close-talk and handset microphones in accuracy because the element is close to the mouth.
• Some ear-piece microphones have a near-field element so it's noise resistant.
• User has his/her hands free.
• User can lean back in his/her chair and talk. (Make sure the microphone cord is long enough so users can lean back, even if their PC is under their desk.)

Problems:

• Most users dislike wearing something or being attached to their PC. Sometimes the cord gets tugged on when the user moves around.
• Difficult to talk on the phone with a telephone handset while wearing the close-talk.
• Slow to put on and take off.

Handset

Benefits:

• Second only to close-talk and ear-piece microphones in accuracy because the element is close to the mouth.
• Some handset microphones have a near-field element so it's noise resistant.
• Users don't like talking to computers, and don't like it when colleagues walk by their office and see the user "talking to themselves." With a handset, users feel like they're talking to a person (or at least an answering machine), and people walking by just see someone talking on the phone.
• Some handsets have switches that allow the user to turn speech recognition on/off.
• Of all the microphones, users are already trained to use this one.
• Easy to pick up and put down.
• User can lean back in his/her chair and talk. (Make sure the microphone cord is long enough so users can lean back, even if their PC is under their desk.)

Problems:

• Users have to hold the handset, which can get tiring if it's used for long periods of time.

Clip-On

Benefits:

• Moderate accuracy because it's less than 30 cm from the mouth.
• User's hands freed.
• The microphone element is out of the way.
• User can lean back in his/her chair and talk.

Problems:

• Most users dislike wearing something or being attached to their PC. Sometimes the cord gets tugged on when the user moves around.
• Slow to put on and take off.
• Users don't know exactly where to clip the microphone on.
• Not good in a noisy environment.

Desktop

Benefits:

• Moderate accuracy if it's positioned less than 30 cm from the mouth.
• User's hands are freed.
• Cheap.

Problems:

• The user has a "stick" pointing towards him, and usually doesn't like this since it's visually distracting. Most users will reposition the microphone so it points upwards, which reduces accuracy.
• Users don't always know how to position the microphone. Some will put it 90+ cm away, where accuracy will be poor. The best accuracy is when the microphone is about 15 cm away.
• Users have a tendency to lean into the microphone when they speak. This is unnecessary. When users lean it adds extra effort to use speech recognition. Make sure users know not to lean in.
• Some users will lean in, and speak to the microphone with their mouth about 3 cm away from the element. This produces poor accuracy.
• Consumes desk space.
• Not good in a noisy environment.

Handheld

Benefits:

• Second only to close-talk and ear-piece microphones in accuracy because the element is close to the mouth.
• Some hand-held microphones are near-field element so they're noise resistant.
• Users have seen plenty of performers using these microphones and already know how to use them.
• Some handheld microphones have switches that allow the user to turn speech recognition on/off.
• Easy to pick up and put down.
• User can lean back in his/her chair and talk. (Make sure the microphone cord is long enough so users can lean back, even if their PC is under their desk.)

Problems:

• Users feel like a rock-star.
• Users have to hold the microphone, which can get tiring if it's used for long periods of time.
• Microphone tends to roll when put down.

Built into computer/monitor

Benefits:

• Nothing to plug in.
• User's hands are free.
• The user doesn't necessarily know where the microphone is so they don't lean into it.

Problems:

• Low accuracy unless the user is unusually close to the monitor.
• Not good in a noisy environment.

Rest on top of monitor

Benefits:

• User's hands are free.
• The user doesn't necessarily know where the microphone is so they don't lean into it.

Problems:

• Low accuracy unless the user is unusually close to the monitor.
• Not good in a noisy environment.

Keyboard

Benefits:

• User's hands are free.

Problems:

• Very low accuracy because of the typical position of the keyboard.
• Users might lean into the microphone to talk to it.
• Microphone picks up keyboard clicks.
• Not good in a noisy environment.

In remote control

Benefits:

• Necessarily wireless.
• If the remote is used to control an entertainment PC from the user's couch, it's a good place to embed the microphone.
• Remote can have a push-to-talk feature.

Problems:

• Moderate accuracy if the user keeps the microphone about 30 cm from his/her mouth.
• Users have to hold the microphone, which can get tiring if it's used for long periods of time.
• Users don't know where to position the remote for best accuracy, so they may lean into it.
• Batteries.

Additional Features

On/off switch, push-to-talk

Microphones can have an on/off switch built in that starts/stops recognition. Alternatively, the microphone can remain off except when the user presses a button down, talks, and lets go to stop talking.

Benefits:

• If the user has his/her hands already on the microphone, a button provides a quick way to turn speech recognition on/off quickly and easily. Otherwise the user has to hit a key on the keyboard.
• Having a switch on the microphone is intuitive.

Problems:

• Cost.

USB

Most microphones plug into the PC with a 1/8" stereo mini-jack. The A-to-D conversion is done internal to the PC. Alternatively, microphones can plug into the USB port on newer machines.

Benefits:

• Users can't plug the microphone into the wrong place. Users sometimes plug mini-jack microphone plugs into their speakers jack. The Microphone Setup Wizard alleviates this problem.
• Because the A-to-D is separated from the D-to-A, the PC can record and play audio at the same time, even at different sampling rates.
• Slightly better accuracy because the A-to-D is no longer in the electrically noisy chassis of the PC.
• USB microphones can have an on/off switch or push-to-talk that turns speech recognition on/off. The on/off switch on analog microphones can only mute the audio going to the speech recognizer, but the recognizer still has to process audio.

Problems:

• Expensive.
• Not all PCs have USB.

Wireless

Any kind of microphone can be made wireless. Wireless microphone have the following:

Benefits:

• No cords attached.

Problems:

• Slightly lower accuracy because of the RF transmission.
• Batteries.
• The user's "conversation" with his computer is being broadcast, and is no longer private.
• Problems with several wireless devices are used in the same area.
• Expensive.

Links to Microphone Companies