How to improve audio quality?
Thijs Donders, 26 July 2018
Thijs Donders, 26 July 2018
Often our clients ask us why the accuracy of their automatically generated transcripts varies. It can be a consequence of the audio quality. The extent to which your audio file can be automatically converted into text is directly related to the quality of your audio. Good audio quality will definitely speed up the transcription process! Do you want to save yourself time and guarantee better transcription results using transcription software? Below, you can read how to improve audio quality in 4 simple steps.
Below we will discuss the above points in more detail.
Sound quality is greatly influenced by the distance between the speaker and the microphone. If the speaker is too far away, the microphone will not pick up all sounds properly and some parts may get lost. If the distance is too short, you will hear the speaker breathing into the microphone. The perfect distance depends on the microphone; often, the ideal distance is around 10 centimeters.
If you use your phone, holding it in front of the speaker’s mouth gives the best result. If that is not possible, the phone should be placed on the table right in front of the speaker. Moreover, take your phone case off so the microphone is uncovered. The transcription should go easily then!
The audio quality improves enormously when most of the background noise is eliminated.
Technically it is never completely silent, even in the quietest environments there will be some sounds. It is therefore impossible to have complete silence anywhere, but we do have a few tips to make sure it is as quiet as possible at the moment of recording:
Of course, the quality of the audio depends greatly on the quality of the microphone. With microphones, it is often true that more expensive microphones also have better quality. Fortunately, there are also cheap microphones for recording good quality audio, if only because they ensure that the speaker and the microphone are at the right distance from each other.
There are different types of microphones, these are:
The lavalier is excellent for interviews. Lavaliers provides better recording quality than a telephone and ensures that there is an optimal distance between the speaker and the microphone. Another advantage is that lavaliers are often equipped with two heads, so you do not need to move the microphone for another speaker during an interview.
A table microphone is a microphone that can be placed on the table between the speakers. Most table microphones provide better recording quality than a telephone. A table microphone can be useful in a conversation with several speakers. If the speakers are in different directions of the microphone, it is important that the polar pattern of the microphone is Omni Directional (more on this later).
Currently, there is voice recording software available for almost every smartphone. Because of this, the smartphone is the most accessible microphone in this list. The recording quality is pretty good for most smartphones, but it does improve the quality if you keep the phone close to the speaker and do not put it on the table.
Most laptops have a built-in microphone, this microphone can also be used for recording interviews. The laptop and phone are both good options if you do not want to invest in a separate microphone. However, for recording interviews, we recommend using a smartphone over a laptop. This is because a smartphone is easier to use and records in better quality audio.
A voice recorder, often called a dictaphone, is an excellent microphone to be used for recording interviews. The quality of the recordings is usually very high in a voice recorder. Also, with a voice recorder, the quality of the recording improves enormously when you keep the voice recorder near the speaker instead of putting it on the table.
There are different types of microphones that record sound from different directions (also called polar patterns).
For interviews, a Figure-of-Eight is the best choice, because it absorbs the same amount of sound on both sides of the microphone. A Figure-of-Eight also records less background noise than an Omni Directional. However, Figure-of-Eight microphones are often a lot more expensive.
Research on the accuracy of our software with different microphones reveals major differences, as can be seen in the table below. Word Error Rate means the percentage of errors that our software makes. For example, a Word Error Rate of 10% means that there are on average 10 errors for every 100 words. Find the results of the research below:
|MICROPHONE||WORD ERROR RATE|
|Lavalier (a clip-on microphone) + telephone||10% – 20%|
|Premium smartphone on the table||20% – 30%|
|Premium smartphone in your hand||15% – 25%|
|Budget smartphone on the table||30% – 80%|
|Budget smartphone in your hand||20% – 50%|
|Laptop||30% – 50%|
|Table microphone||10% – 40%|
As you can see above, there is already a significant difference between putting your phone on the table and holding it in your hand. Furthermore, the quality of your microphone is extremely important. With a lavalier, the quality of the audio can be significantly improved, and the Word Error Rate reduced.
We have selected lavalier and table microphone options with high sound quality for you, which you can use with your smartphone:
Besides that, it is not quite correct to interrupt each other, this also confuses our transcription software. That is why it is important to let each other finish your sentences so our software can do its job as well as possible. Furthermore, our software has some trouble with heavy accents. Of course, it is difficult to do something about an accent, but it is an enormous help to try to talk as accent-free as possible. By following these tips, we can best convert your audio into text.
As discussed above, it is actually very simple to improve the quality of your audio files. First, it is important to keep about 10 centimeters between the speaker and the microphone. Secondly, it is important to eliminate background noises, so unplug any devices that can produce sound and tell everyone near you that they should be quiet. Thirdly, it is important not to interrupt each other. Finally, the quality of the sound depends greatly on the quality of the microphone and the type of microphone.
If you follow these tips, the quality of your audio files will improve enormously, so we can better convert them to text and you have to make fewer adjustments to your automatically transcribed texts!
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