Is there any easy way to listen to the input on a Mac?

For example, assume I have a microphone hooked up to the input (i.e. line in) of my Mac, and I have headphones hooked up to the output of my Mac: is there any way that I can hear what I say in the microphone through the headphones?

This is very easy in Windows XP: simply go to the sound settings for recording devices, check "select" on the line in, and increase the volume – this makes it so you can hear what is said into the microphone.

It has to be in real time; a solution where you record the input and then playback the output later doesn't help.

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9 Answers

Take a look at Rogue Amoeba's LineIn. It is a free application which will allow you to do what you want.

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With 10.6 (and newer, AFAIK) you can launch QuickTime Player.app and choose File -> New Audio Recording. Then just turn up the volume control that is part of the window that appears. You might hear a bit of white noise when there's no sound and the volume is all the way up but the Rogue Amoeba app does the same thing.

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As originally suggested by qu1j0t3, Apple's "AU Lab" provides the ability to listen to the audio input in real-time. (Well, nearly in real-time; for me there is a slight delay from input to output.)

• Download from here: (thanks alex r. g.!)
• Direct link:

(If those links die, it can also be downloaded from Apple Developer Tools, which may require an Apple Developer account.)

• Download from here: > search for "AU Lab"
• Direct link:

Usage:

In the Document Configuration window, select the existing "Stereo In/Stereo Out" configuration. (If the Document Configuration window is not already open, click File → New to open it.) Then click the Create Document button in the bottom right corner.

In the new "Untitled" window that opens, ensure the icon at the bottom says "Audio Engine Running" (or click to toggle if it says "Audio Engine Stopped"). If necessary, adjust the system's overall input and output volume settings in System Preferences → Sound → Input.

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You can also use Garage Band. Choose for example the Acoustic Instrument template (the default audio track in it has no effects) and set monitor to on.

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If you're using an older Mac, the application Audio MIDI Setup.app in the Utilties folder (found in the Applications folder) allows* the ability to pass-through input straight to your output.

To do so; click on your input device and then check off the "Thru" checkboxes to pass audio through. However oddly enough I've never seen anyone to get it to correctly work on an Intel based Mac, I've had it work great on some PowerBook G4s however.

The better alternative is to use Rogue Amoeba's LineIn (as said by Richard Hoskins). Personally I use this and find it easier to use.

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Another option is "AU Lab" in Developer tools (Developer/Applications/Audio/AU Lab).

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If you want to use the terminal, you can install sox (i.e. with Homebrew brew install sox) and then run

sox -d -d

Here, -d means "default audio device", and this command specifies it for both the input and the output, i.e. microphone and speakers/headphones.

You can decrease latency by decreasing the buffer size (default 8192), try what works for you:

sox --buffer 1024 -d -d

2020 Update:

Best way:I have an mbox with a condenser mic. When I run the audio thru that, 0 delay and your headphones can be true monitors. I bought a Snowball for ease tho, its a lot to setup.

My solution:Garage band had the best delay for me. Open garage band in the background. Create an audio track and turn on the monitor icon on the track. Shut off any effects.

Easiest solution:Audio Hijack was next best. Its 60 bucks but seemed like cool software if you had more to use it for. Good be noticeable delay. .

Free:* Sox but it had a surprisingly long delay for a CLI. See @billfraser's answer

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I tried several things and was getting pretty frustrated until I discovered an old 2010 article by Adam Dachis about using AudioMonitor, part of MTCoreAudio’s developer package for Apple products. (You can download MTCoreAudio for Mac for free at .) It works perfectly on my Powerbook (OS El Capitan). Once opened up, just click on "Play Through". Now when I travel and my wife or I want to watch Hotel TV while the other doesn’t, to use headphones (you'll need to bring along a fairly long mini plug cable) she or I can just plug my laptop into the TV’s “speaker out” port via the computer’s line in mini plug port (my laptop has two mini ports, unlike the newer models) and the headphones into the computer’s audio out port. The sound is perfectly synched to the TV (no delay) and to avoid any irritating white noise in the background we simply unplug the computer’s power cord and run it on battery mode. Much better than Quicktime (delay) or any other trick I tried.

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