The CEL633A meters include the Voice Notes and Audio Recording options, which provide the following features:
Voice Notes are used purely to help you to identify your measurements. They are not recorded during the actual measurement process, but usually just before starting the measurement.
After pressing Run you will be asked to record your note, which can be up to two minutes long. Press the Rec key and speak into the meter's microphone. After recording the meter will automatically start the measurement.
Pressing Exit will skip this process. You can go back to the measurement later and record the voice notes before downloading to a computer.
Voice Notes are kept with the measurement when downloaded to ensure that you can use the note to identify the measurement.
This process records the actual sound at the same time as it is being measured. The purpose is usually to help identify the source of high noise levels. Most logging sound level meters provide you with a graph of the level over time. This is very useful, but does not give a way of finding out what caused the noise - car, plane, factory, shouting, etc.
You don't usually want the audio for the full measurement period - too much data and too much to listen to, although the meter can be set to do this. There are three ways to trigger the recording:
1. Sound Level
The meter can be set to start recording when a certain level (Fast, Slow, Leq or Peak) is exeeded for a given period of time, and to stop recording when the level falls below a level for a given period. In the example to the right, the audio will start recording as soon as the Fast sound level exceeds 80dB and will stop after the level falls below 60dB for five seconds.
2. Markers - On Demand Recording
This meter has four "Markers" available. While a measurement is running you can press one of four keys to mark a section of measurement. For example, if you are interested in vehicle noise you could press Marker 1 when a car passes, Marker 2 when a bus passes, Marker 3 for a motorcycle and Marker 4 for a train. The meter can be set to record the audio whenever a Marker button is held down.
3. External Trigger
No external trigger is supplied with the standard meter so please contact NoiseMeters for more details. An example of the External Trigger can be seen with the Noise Nuisance Recorder, which is used to monitor noisy neighbours. When the external button is pressed it triggers the CEL633A sound level meter to record audio.
Often you need an audio recording to include a short period of time before the level is exceeded (for level triggered recording) or before the marker is selected. A pre-trigger can be set to record up to 10 seconds of audio before the event.
Voice Notes and Audio Recordings can be played back on the meter itself or on a computer after downloading.
Playback on the Meter
Both Voice Notes and Audio Recordings can be played through headphones or speaker system directly from the meter itself - ideal if you want to make quick checks while still on site. Measurements with audio recordings are clearly indicated in the memory recall list. The example to the right shows the playback of a Marker (on demand) recording along with the main measurement parameters.
Please note that the meter does not have a built-in speaker. Headphones or a small speaker system can be plugged into the jack-socket at the base of the meter.
Playback on a Computer
For the best results the measurements should be downloaded with the Insight software. The CasellaDrive software can also be used, but this does mean you have to manually deal with the WAV files and link them with the measurements yourself.
The example here shows the noise profile graph. The section highlighted indicates where an audio recording was made.
The player controls under the graph can be used to play the audio through the computer's speakers.
Audio recordings can also be listed by time in a table and played from there.
The Class 1 sound level meter is available alone or as part of a Kit, which includes Meter, Calibrator and Peli Carrying Case.