Why Aren't My Dynamically Inserted Ads the Same Volume as My Podcast Episodes?

Occasionally podcasters may experience a sharp difference in volume between dynamically inserted ads and the baseline volume of their podcast episode. This can result in an unpleasant listener experience due to dramatic transitions between the ads and the episode. To understand why this happens, we need to understand the difference between "loudness" and "volume."

Acoustics focuses on "loudness" rather than "volume." Loudness is the measurement of how intensely our ears perceive a sound. Volume measures the strength of vibrations from a sound. Loudness from audio such as your podcast episode is measured in LKFS (also called LUFS).

Apple Podcasts recommends that your podcast audio is mixed so the overall loudness remains around -16 dB LKFS, with a +/- 1 dB tolerance, and that the true-peak value doesn’t exceed -1 dB FS. That unpleasant transition in volume between dynamically inserted ad and podcast episode occurs when the episode loudness deviates significantly from Apple's recommendations. If you are unsure of your episode loudness, you can quickly measure its LKFS/LUFS using online tools like this one.

Our Dynamic Ads Insertion system analyzes all the audio ads in our inventory, identifies ads with "high" loudness, and re-encodes them at -16 dB LKFS, as per Apple's specs. This results in a pool of audio ads in our inventory with normalized loudness.

We highly recommend podcasters encode their episodes with an overall loudness of -16 dB LKFS, as per Apple' specs to minimize (or even eliminate) this "transition" effect. Following Apple's recommendations on audio levels will also improve the overall listening experience.

Reference: https://podcasters.apple.com/support/893-audio-requirements (section "Audio levels").

Pro Tip: Some podcasts using dynamic ad insertion will include a jingle or brief sound (also known as a "bumper" or "stinger") before or after the timestamp where ads are supposed to be inserted. This is a good practice, as it can further help in creating a cohesive audio experience when ads are inserted.

For instance: Advertisement + short intro bumper + host starts speaking. Even a 2 or 3 second clip of audio will do the trick!