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Microphones for speech recognition

by Lynette Penney | Oct 18, 2012

The quality of the microphone is important when recording for a speech recognition program. However, this does not always mean you need to go for the most expensive option – it all depends on the situation. This is a summary of the main options.

Introduction

When used in a quiet environment, many of the cheap microphones supplied with voice recognition software packages work well enough to demonstrate the potential of speech recognition. However, we recommend that you purchase a high quality microphone for greater durability and to obtain best results from your software.

The best results for speech recognition are gained when the microphone is kept a consistent distance from your mouth. For this reason we recommend headset microphones for dictating to your PC. If you are using a portable dictation machine or a MiniDisc recorder you may want to use a stub microphone which we will deal with at the end of this article.

Which Microphone Should I Use?

We would recommend using the following;

  • A noise-cancelling microphone (which samples background noise and filters it out);

as these are less likely to be affected by noises other than your voice, and consequently give better results.

Each user will have different likes, dislikes and reasons for choosing one microphone in preference to another; a frequent factor in microphone choice is comfort. It is entirely dependent on the shape of your head which microphone you find most comfortable.

Testing Methodology

We test a wide variety of microphones on a range of different computer systems and with both the current market leaders in speech recognition software, Dragon NaturallySpeaking and IBM Via Voice (please note that at the time of this update, July 2006, Via Voice is not compatible with Tiger 10.4.6, but will work on earlier Mac OS):

  • We try to keep our testing standardised to ensure that results are as accurate as possible.
  • For each system and each different microphone we do a general check of the microphone using the audio set up wizard, and then follow the basic enrolment procedure.
  • We then dictate a standardised text into the application’s word processor and also into Microsoft Word, and note the number of mistakes.
  • Then we correct the dictation, save the user files, repeat the process and note the results again.

Results

The following Headset Microphone gave good results during testing:

Andrea Electronics (Active Noise Cancelling) NC-181VM USB

The Andrea Electronics NC-181VM USB uses noise cancellation. It has a flexible microphone boom, and a comfortable earpiece with stainless steel adjustable headband which is suitable for those with a larger head.

Stub Microphones

These give better sound quality, and therefore better recognition, than built-in microphones in portable note-takers like the Dragon Mobile / Voice IT recorder and the Olympus DS 150. The Sony ECM-DS70P is a reasonably priced stereo microphone suited to lecture theatres. You will also need a microphone if you are using a MiniDisc recorder. You can use a headset microphone such as the Andrea, although you may find a stub microphone more convenient and more suited to the pocket nature of your recorder.