Audacity recording shorter than Zoom recording

Best team,

I made a live recording with Audacity and with a ZOOM H2 Flash recorder.
The recording with Audacity was made with a Macbook Pro retina 15" Mid 20017 Mac Os 10.14.

The strange thing is the Audacity recording is 2.5 seconds shorter than the Zoom recording.
At the same time we did a 2nd recording with a Zoom H4n Pro recorder and it was the same as the H2.
We also edited the recording of the Zoom H4n in a video movie. That was lipcynchronous.

How is it possible that the two shots are not the same?

The top stereo track is the live Audacity recording.

With kind regards,
Translated with

Beste team,

Ik heb een live opname gemaakt met Audacity en met een ZOOM H2 Flashrecorder.
De opname met Audacity is gemaakt met een Macbook Pro retina 15” Mid 20017 Mac Os 10.14.

Het vreemde is de Audacity-opname 2.5 seconden korter is dan de Zoom-opname.
We hebben tegelijkertijd een 2e opname gedaan met een Zoom H4n Pro recorder en die liep gelijk met de H2.
Ook hebben we de opname van de Zoom H4n gemonteerd in een videofilm. Dat was lipcynchroon.

Hoe kan het dat de beide opnames niet gelijk lopen.

De bovenste stereotrack is de live Audacity opname.
Met vriendelijke groet,

Schermafbeelding 2019-06-09 om 12.05.31.png

The clock speed in either the computer sound card, or in the Zoom, or both, may be slightly off, so they are not recording at exactly 44100. My guess is that the Zoom will be pretty close to 44100 Hz, and the computer sound card is running about 1.6% slower. In “normal” use of a computer, no-one is going to notice if their sound card is running a couple of percent too fast or two slow - it’s only if compare it side by side with another device that the difference becomes apparent.

If you want to stretch one track to match the other, use the “Change Speed” effect. Change Speed and Pitch - Audacity Manual

Now you know what this is.


This is a clapboard. You write down the show and scene info. At the beginning of the shoot, you stand so the camera can see it and the sound services can hear it. Yell “Camera Mark” and close the clapper. The truly obsessive will include an End Mark where you hold the board upside down at the end and yell “End Mark” (bang!).

Match up the action with the “bangs” in editing.

Be sure you use a Dry Erase Marker, If you use a sharpie, you will be down there later with acetone and rags trying to remove the ink.

Note that if you always use the same equipment, chances are good you will only need the end mark once, so see how far off everything is. The correction percentage should stay the same.

I would believe the Zooms, too. Their whole reason for existence is to make good sound. The purpose of the soundcard is to be cheap and inexpensive.