Every so often, sometimes once a day, sometimes two or three times in ten minutes, my audio will reverb at 100% for about 3 seconds. It's very random, with no clues it's about to happen.

This has happened while watching youtube, while using Reason, and while using Logic Pro X, so I don't think it's the applications. It didn't start until Catalina.

The system, an iMac (Retina 5K, 27-inch, Late 2014), is running macOS 10.15.3, the sound is going through a Focusrite Scarlett 18i8 (first edition), which I've been using for years now with little problem. I don't have any other devices, virtual or physical. All inputs and outputs go through the focusrite, and the microphone is selected off, and nothing is registering on meters.

Does anyone have any insights? It's not the end of the world, but it certainly is annoying.

  • Is this howl-round from built-in mic to built-in speakers, or is any other I/O involved at all? Can you see it metered on the Focusrite, or in Logic?
    – Tetsujin
    Feb 15, 2020 at 13:20
  • Does it happen if you remove the Focusrite from the audio chain?
    – IconDaemon
    Feb 15, 2020 at 13:49
  • The microphone is off, and doesn't show up in meters. I don't recall seeing this in meters, but it's just random enough, and short enough that I'd miss it.
    – Hack Saw
    Feb 15, 2020 at 14:17
  • I'm going to have to try removing the focusrite, I guess. I was hoping that someone else had experienced this before.
    – Hack Saw
    Feb 15, 2020 at 14:18

1 Answer 1


The tool I would start with is MicroSnitch if no one has a hunch or guess what would enable intermittent sound input.

Another thing that's quick to check is Siri. That could trigger a short and intermittent mic active event (and doesn't show in the Microphone section/tab of Security & Privacy). Other apps should show in system preferences for all other apps entitled to mic input before you redo or tear down the main sound processing setup.

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  • 1
    Ooooo, that's an interesting idea...
    – Hack Saw
    Feb 15, 2020 at 14:22
  • 1
    Oh well, no, Siri is strictly mouse or keyboard triggered. Supposedly.
    – Hack Saw
    Feb 15, 2020 at 14:24
  • @HackSaw Sounds good - I uploaded a screen shot of the place other apps should show if they get to listen to the sound input / mic on Catalina. With software ruled out, it might be the hardware and not the OS. Please post an answer when you find it - a pretty interesting puzzle you have proposed.
    – bmike
    Feb 15, 2020 at 15:19
  • Yep. my first thing is unplugging the mic, in case something is activating it. Frustrating that I have to wait for it to happen...
    – Hack Saw
    Feb 15, 2020 at 19:12
  • Sad. I've had a couple of events in the last couple of days. That said, it did take that long, so that's something...
    – Hack Saw
    Mar 19, 2020 at 4:54

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