Hajime Nagai

Both smartphones and laptops have built-in microphones, but do you need a dedicated microphone?

This article is aimed at people who use speech recognition for work or other purposes.

Have you ever seen someone nearby using speech recognition and felt puzzled by how it behaved?
We are now seeing speech recognition services being used in a variety of situations, such as built-in speech recognition in smartphones and AmiVoice products. But have you ever seen a situation where the machine reacted strangely, as if it couldn't hear you properly? Even though the person's voice sounds fine to you.

One factor contributing to misrecognition is that there are times when the voice heard by people differs significantly from the recorded voice. When you want to effectively utilize speech recognition in business operations, it is essential to maximize accuracy as much as possible, making the selection and usage of microphones for recording critically important.

Choosing the right microphone is crucial for utilizing speech recognition!

Recently, we often hear that speech recognition technology has advanced to the point where the recognition rate exceeds 90%, but if you feel that the accuracy is not as high as you would expect, then you should take a look at your microphone.

Points to consider when choosing a microphone

Let's look at microphone catalogs to see what kind of microphone to choose for speech recognition. However, the specifications listed in the catalog are for reference only. The sound recorded will vary depending on various factors, such as compatibility between the devices, the service being used, and the limitations of the OS and software being used. No matter how good the specs are, the actual sound may be terrible, so please check the following points.

1. Directivity
   A unidirectional  microphone is recommended for focused recording of only your voice without picking up surrounding sounds.
2. Sensitivity
   When using speech recognition in noisy environments, better results can sometimes be achieved by selecting a microphone with low sensitivity and speaking with the microphone positioned close to your mouth. This is because it becomes less susceptible to picking up surrounding noise, allowing focus to be placed on your voice. However, when using a microphone with low sensitivity, be sure to speak with a slightly raised voice. Some models with sensitivity adjustment capabilities built into the microphone itself are also available on the market, which are very convenient.
3. Type
   Please use what is commonly referred to as an electret condenser type.  Audio from bone conduction or throat microphones is special in nature and unfortunately is difficult to use for speech recognition purposes.
4. Shape
   The best microphone is one where the microphone body is attached to the end of a long arm called a microphone arm , allowing it to be moved and adjusted to the mouth. There are also microphones that, through ingenious directivity design, can be used as if they were close to the mouth even when positioned at a distance.
5. Connection method
   When connecting a wired microphone to a PC, we recommend using a USB audio adapter . This makes the system less susceptible to electrical noise and other interference. When selecting a Bluetooth microphone, please choose a product that can record in WIDE BAND (16kHz) , which is often indicated as HD VOICE.

How to use the microphone and speaking tips

Even if you have a good microphone, if you don't use it properly, you won't be able to get the most out of it. Here are some tips to keep in mind when using it.

1. Check that the microphone and mouth are positioned appropriately. Directional microphones can make the sound extremely quiet if you don't speak directly into the microphone.
2. Even though there is a microphone connected via Bluetooth, are you speaking directly into the device? Make sure that the microphone you are speaking into is the same as the microphone the app is using.
3. Even if you think you are speaking in a quiet place, there may be surrounding noise, background music, voices, and room reverberation. If you listen to the recorded audio, you may realize that it is surprisingly loud.
4. When using in a noisy environment, lower the microphone sensitivity and hold the microphone closer to your mouth. If the surroundings are noisy, you may be speaking loudly without realizing it, so be careful not to speak so loudly that the microphone input meter swings off the scale.
5. In fact, sometimes the popping sound when opening the mouth or breathing out through their nose at the end of a conversation can be recorded. In such cases, using a microphone with a windshield (microphone cover) can reduce this.
6. Be careful if you have a habit of saying things like "huh?" or "ah" without realizing it when you speak. Adding an extra word at the beginning can sometimes result in the word being converted into an unintended word.
7. Do you speak slowly, as if you were teaching a child? Speaking slowly will cause the sound to break up, further reducing accuracy. Try speaking as you would in normal conversation.

Others

Depending on the type of microphone and OS, features such as echo cancellation and AGC (auto gain control) may be available. These make it easier for people to hear your voice during a call, but while they may make it easier for people to hear, they alter and process incoming audio, which can degrade speech‑recognition accuracy, so we recommend disabling these settings for the time being.

A dedicated microphone is recommended for speech recognition

　　　

At Advanced Media, we are also developing dedicated microphones that can capture the clear voice that is essential for speech recognition. They are also available on Amazon, so please feel free to give them a try.

Use the microphone correctly to make speech recognition more convenient!