crackling when recording voice [SOLVED]

[LukeB]

Hi guys,
I've recently started recording church sermons.
Everything starts out fine and then some time in (say 20 mins or so) a crackling can be heard, and as time goes on is slowly gets worse. The crackling is only present when the voice is there (i.e. not in the silences). The audio is coming straight from the mixing desk and the crackling is not heard through the sound system.

Here is a sample of what I'm talking about: http://elfuzzo.websiteconnection.com.au ... sample.wav

Attached is a screenshot of some of the above sample - spikes can be clearly seen although the crackling is happening in throughout the whole thing and not just on the spikes.

crackling_audio_screenshot.png (26.75 KiB) Viewed 7022 times

I'm using Audacity 2.1.2 on El Capitan and all other programs are closed while recording.
If anyone has any suggestions to help with this it would be much appreciated

[kozikowski]

The download gives me a File Not Found.
What's the computer? I'm typing this on a Mac Mini.

Koz

[LukeB]

Sorry about that - I've just fixed the sound sample link.

I'm using a Macbook Pro for recording.

[cyrano]

Download works here and now...

The audio is coming straight from the mixing desk and the crackling is not heard through the sound system.

Sounds like loss of sync. USB?

What's the mixing desk and the interface between it and the computer?

[LukeB]

I'm using one cable between the mixer and the laptop - no USB in between.

It's a 2xRCA <===> 3.5mm stereo cable connecting from an RCA output on the desk straight to the line-in on the laptop.

[Gale Andrews]

It will be power saving, buffer settings, mismatched sample rates between Audacity project rate and the Line-In in Apple Audio MIDI Setup, or all three.

See http://alphamanual.audacityteam.org/man ... ac_crackle. Don't look elsewhere in that Manual because it is our development manual. After Audacity 2.1.3 is released the link will be http://manual.audacityteam.org/man/faq_ ... ac_crackle.


Gale

[LukeB]

Hi Gale, thanks for that.

So I've made sure the MIDI line in settings and Audacity sample rate & bit depth match each other (44.1kHz and 24-bit), and I've selected "prevent app nap" for Audacity, so I'll see how things go this weekend.

Since the first week's recording was fine (no crackling for any of it) I'll leave the buffer setting as it is after making the above changes, and if it's still causing dramas I'll change that for next weekend.

Thanks for your help guys - I'll let you know how things go after Sunday.

[LukeB]

Thanks guys - that seems to have fixed the problem