Audio Digitisation QC Quiz #2

Question 5 (the final question!)

The following audio file was created by Indiana University:

Above audio file credit: Indiana University
What can you hear happening at 6 secs into the recording compared with the audio before it?
Greater clarity and increased volume
Yes, the azimuth has been adjusted so that all the higher frequencies in the recording can be heard
Increased volume
Yes, the volume appears to go up but something more is happening
Increased low frequencies
If we were living in the upside down maybe…


As Indiana University explain:

‘The track begins before the azimuth is adjusted and you will hear the following:

About (0:06)—the adjustment is made. You will hear increased clarity and an increase in level (volume).
Around (0:15)—azimuth is set back to the original (incorrect) setting
Around (0:23)—azimuth is adjusted again


Changing the azimuth is like the audio equivalent of focusing a lens. Instead of either side of that focused point being blurry, with audio it sounds muddy. This is because the higher frequencies are not being picked up and made audible.

The angle of the recording head can be wildly different on recording devices. So when it comes to playing these tapes back you can make an adjustment on the machine to reposition the head to match the same angle on the recording. That is what’s happening 6 seconds in. Someone is fine-tuning the azimuth angle so that all of the signal available can be heard.

After cleaning and maintaining playback equipment, setting the correct azimuth for each recording is one of the most important things to do when digitising audio. We play the tape, listen carefully and use audio scopes to make sure the azimuth is correct. If all the other settings are also correct we then rewind the tape and then we’re ready to record with the correct azimuth set from the start.

Above is an example of what a Phasescope looks like with 4 recordings running all at once.

Above is an image of an azimuth modification dial added to a Studer Open-reel machine.

Above is an image of a hex screwdriver being using to adjust the azimuth on a audio cassette tape deck with a modified hole for access.


For further info please check out these excellent resources:


IASA Special and Technical Publications


For more on the British Library’s Unlocking Our Sound Heritage project:

UOSH Project

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