Podcast test pack: tone, pink noise, sync blip and slate

By James Jones, founder of Granary Digital · Updated 5 November 2026

A test pack is three short files, a spoken slate and one habit: play the tone at the start of every session, before anyone speaks. The three files are supplied as 48 kHz, 24-bit WAV, 30 seconds each, so they play in any editor and most players. The tone and pink noise are at -18 dBFS RMS, so a peak-reading meter shows the tone at -15. Each one answers a single question, and together they cover the set-up that most often goes wrong on a recording day.

Before you press record

Line up the chain with the tone first, then set each microphone from the voice. Do this for every session, including the ones that feel routine. A few seconds of recorded tone at the head of the files tells anyone who opens them later where the chain was set.

What each file is for

• 1 kHz tone. A steady sine wave at 1,000 hertz. It lines up the chain, from desk or interface to recorder and camera, so that a known signal reads the same value on every meter.
• Pink noise. Noise with equal energy in each octave, so it sounds even across the range. Play it through the monitors in the room and walk around. Changes in tone at the listening position show the room, not the microphone.
• Sync blip. A file with a 10 millisecond 1 kHz blip every two seconds. Play it into every recorder at the same moment and line the blips up in the edit. For picture, also clap in front of the camera and microphone: on the audio it is a clear spike, and on the picture the hands meet.
• Slate. Not a file in the pack: a spoken card you say yourself at the head of each take: show name, episode, take number, date and the name of the person speaking. It is what lets you find a take months later.

Line up the chain with the tone

1. Send the tone from the desk or interface output into each recorder or camera that takes a feed from it.
2. Set each device's input so the tone reads minus 18 dBFS on its meter, the same as the desk.
3. Record the tone for a few seconds on every device, label it, and keep it with the session.
4. Set each microphone's gain from the speaker's normal voice, and check that laughs and loud moments stay clear of full scale.

The tone does not set microphone gain. That step always uses the person who will speak.

The reference article on alignment levels gives minus 18 dBFS as the digital alignment level and attributes it to an EBU recommendation. It also notes that digital alignment tones are often 997 Hz rather than 1 kHz. If your broadcaster or platform specifies a different tone or level, use theirs and say so on the session sheet.

A worked example

Before a two-person interview, Nadia sends the tone from the desk to the camera and sets the camera's audio input so it reads minus 18 dBFS, the same as the desk. She records twenty seconds of it on both, then sets each microphone from the guests' voices. She then claps in front of the camera and the microphone together, and speaks a slate with the show, episode and take. She saves the tone, the clap and the slate recordings in the session folder with the episode number in the name. When the edit starts, the clap gives her the sync point and the slate tells her which take is which.

Common mistakes

• Lining up the desk but not the camera or the backup recorder, so the copies come back at different levels.
• Playing the tone through a compressor, limiter or noise gate. Turn processing off first, or the tone is no longer a true reference.
• Clapping after the first word, so the sync point is not at the start of the take.
• Leaving the slate off, so the take cannot be found in the edit.
• Testing on the wrong input, or on a muted channel, and believing the level is set.

Where the pack fits

The pack is for the start of a session. The editing order of work guide covers what happens after the recording, and the loudness targets guide covers the final levels for delivery.

If you would rather have a studio run the levels, the Podcast Studio at the barn is booked by the hour from £108 +VAT for a Solo session, or per recorded episode at £395 +VAT on the Classic package.

Sources

• Wikipedia, Alignment level, read 5 November 2026

The picture at the top of this page is an illustration, not a photograph of a client or a real job.