No sound from a source

If a source's sound is missing, there are two possibilities: the sound arrives in the studio and is not let through or not listened to there, or the app does not send any. The level meters on the desk tell you within a few seconds which case it is.

Usually it is a small thing: the source is set to “Stumm” (mute), the fader is down, or you are listening to the wrong bus in the browser.

First: does any sound arrive at all?

Put the source on preview and speak into the microphone or clap. Now look at the level meter.

• The meter moves. The sound arrives. The cause is on the desk or in the listening, that is, in steps 1 and 2.
• The meter stays down. The app sends no sound, or the studio cannot read it. Go on with steps 3 and 4.

1. Muted, or the fader is down

Every input has a fader for the volume and a “Stumm” (mute) switch on the desk. Check both. An input that was muted days ago may still be muted.

If the fader is very far down, the sound is there but can no longer be heard in the mix. Push it up and watch the level meter of the bus the source is on.

2. You are listening to the wrong bus

The desk has two buses: program, which is what is on air, and preview, which is what you are preparing. Each has its own picture, its own sound and its own level meters. With “Mithören” (listen in) you listen to one of the two in the browser.

Two traps:

• The source is on preview, but you are listening to program, or the other way round. Then you hear another source or silence, although everything is fine.
• The browser only plays sound after a click. If you have only opened the page and clicked nothing, it stays silent. Click “Mithören” on the bus you want to hear.

Also check the obvious: your computer's volume, and whether the tab is muted in the browser. What your viewers hear is the program alone. Listening in is only your way of checking.

3. The app sends no audio track

If the level meter stays down, look in the sending app:

• Microphone permission. On the phone the app has to be allowed to use the microphone. Without the permission it often sends only the picture, or a silent audio track.
• Sound source. Is the right microphone chosen? An external microphone or a headset that is no longer connected leaves an empty selection behind.
• Sound muted in the app. Many apps have a mute switch of their own for the microphone.
• Audio switched off completely. In encoders on a computer the audio track can often be deselected, so that only video is sent.

4. The audio codec is not AAC

The studio expects the sound as AAC. If your app sends another format, the picture may arrive while the sound is missing. Set the audio codec to AAC. Stereo at 128 to 160 kbit/s and 48 kHz has proved itself. Other common sample rates work as well.

After a change of the codec the app usually has to reconnect.

5. Sound on one side only

If you hear the source only on the left or only on the right, the microphone is on a single channel. That is common with wireless microphone links and audio interfaces. Switch the input to “Mono”. Then left and right are mixed onto both channels.

A microphone that is on one channel only becomes 6 dB quieter by that. Make up for it with the fader.

6. The sound has gaps

Short dropouts instead of silence are a different problem: then packets are being lost on the link. In that case the “Verloren” (lost) counter rises on the “Eingänge” (inputs) tab. What to do about it is in The picture stutters or breaks into blocks.

In short

Read on

• Mixing sound
• Picture and sound out of sync
• Encoder settings