Recorder controls

Praat for Beginners:
Sound recorder
settings and controls

1. Mono or stereo
2. The level meter
3. Sampling frequency
4. The progress bar
5. The recording and playback controls
6. Name the recording
7. Controls for saving the recording

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1. Mono or stereo

 
The stereo Sound recorder has Stereo selected instead.
  • The choice of mono or stereo recording mode is made while you are opening the Sound recorder. This cannot be changed once the Sound recorder is open.
  • If you change your mind and want the other mode instead, close the Sound recorder, then go back to the New menu in the Objects window.

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2. The level meter

When the Sound recorders open, the space for the level meter is empty except for the warning Not recording. Once you start recording, the level meter comes on and you see one (mono) or two (stereo) green columns moving up and down in step with the momentary amplitude of the signal being recorded. This visualizes the strength of the recording and guides adjustment of the recording level.

Stereo (above left) and mono(right). The only difference is the number of channels being recorded.
 
The more you increase the recording level, the higher the indicator rises (the example is mono, it’s the same for stereo). The indicator shows yellow when you pass the 50% level (6dB sound pressure below maximum, the typical limit for a good recording). Increase the level even more and you will hit the red limit, distorting your recording; the signal overloads the capacity of the sound system and extraneous harmonic components are introduced.  Distortion components will spoil any analysis performed on the recording.
  • In contrast, a very weak signal may be hardly distinguishable from the background noise. The signal/noise ratio will be poor; the signal will sound indistinct and partially masked by the background noise, and analysis programs mght not function so well.
  • Aim to have the indicator just showing yellow now and then for the speech, but never red.
  • However, there are special circumstances when the red limit can be be ignored. For example, you might accidentally knock the table or microphone, producing a brief peak into the red zone. Such moments are wasted anyway, concentrate on getting the speech level right. Similar situations can also occur when recording children who are given toys as a distraction, leading to inevitable sudden bumps and bangs.

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3. Sampling frequency

  • Select the sampling rate by clicking the appropriate button. The sampling frequency selected in the Praat Sound recorders is for both channels, so the selection is the same for both mono and stereo recordings.
  • The sampling rate determines how often the analog to digital converter will measure the sound pressure in the signal.
  • The choice of sampling rate is determined by the highest sound frequency required for the signal. The highest useful sound frequency is equal to half the sampling rate. This sampling rate is known as the Nyquist frequency.
  • In the illustration, a sampling rate of 44100 Hz has been selected. The highest useful sound frequency will then be 22050 Hz.
  • Sound frequencies above the Nyquist frequency are not useful because they contain false tones that are introduced by digital conversion and, worse still, that are reflected down into the useful region where they interfere with the signal. The computer sound system filters out all energy at frequencies above the Nyquist frequency to prevent these tones from intruding into and distorting the recording (this is known as anti-aliasing). Nowadays, the anti-aliasing filter is set automatically (but on older equipment you might find it necessary to set the filter manually every time you change the sampling frequency)

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4. The progress bar

 

The recording progress bar (bottom left corner of the Sound recorders) comes on when recording is activated, and also shows how much of the Sound buffer has been filled. Recording halts automatically once the Sound buffer is full, but you still need to click the Stop button to continue working in the Sound recorder. The progress bar stays on until you start a new recording, and reminds you that you still have an active Sound object to listen to or to save.

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5. The recording and playback controls

The sound controls (bottom left of the Sound recorder window) start and stop recording, and play back the new recording. Click the Record button to start a recording.
Stop recording by clicking the Stop button. Note: if you don’t stop recording yourself, recording will come to a halt anyway once the Sound buffer is full; if that happens, you still need to click the Stop button, in order to continue working with the Sound recorder.
Click the Play button to listen to the new recording.
Note that the [Esc] key (back left corner of your keyboard) does not stop playback in the Sound recorder. Playback runs on until the end of the recording.

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6. Name the recording

You can give a name to your new recording, in the name box (bottom right corner of the Sound recorder). This name will subsequently be used to identify the recording in the Objects list in the Objects window. The name “Untitled” will be used if you don’t provide a name of your own.

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7. Controls for saving the recording

There’s a group of buttons in the bottom right corner of the Sound recorder, for finishing the task of recording. Click Save to list and the new recording will be transferred to the Objects list in the Objects window with the name taken from the name box. The default name “untitled” will be used if you don’t provide a name.

The Close button will close the Sound recorder, destroying any recording that happens to be there. Make sure you have saved it as a sound file or transferred it to the objects list, if you want to keep it. Alternatively, you can use the Save to list & Close button, which combines the two functions in one click

 
The new recording is listed as a Sound object in the Objects window.You can rename it here in the Objects window if you wish
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© Sidney Wood and SWPhonetics, 1994-2014

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