Audiobook industry standards

My audiobook productions meet the following criteria and are compliant with ACX, Audible, Amazon and iTunes requirements.

  • consistent in overall sound and formatting.
  • free of extraneous sounds such as plosives, mic pops, mouse clicks, excessive mouth noise, and outtakes.
  • include opening and closing credits that match the title’s cover art.
  • include a retail audio sample that is between one and five minutes long.
  • 0.5 to 1 second of room tone at its beginning and 1 to 5 seconds of room tone at its end.
  • Total RMS level between -23dB and -18dB RMS.

My usual total RMS level is between -22.9dB and -22.7dB. This is at the lower end of ACX specification which is designed to give maximum clarity across all listening devices. Staying at the lower end gives a greater amount of dynamic range, whilst still remaining clear.

I normally leave around a 1 second gap at the start of a chapter and a 3 second gap at the end, adding up to a total of 4 seconds’ gap between chapters. All paragraph or similar breaks within the chapter are never more than 3 seconds to give the listener a consistent experience.

  • peak values no higher than -3dB.
  • noise floor no higher than -60dB RMS.
  • 192kbps or higher 44.1kHz MP3, Constant Bit Rate (CBR).

I can also provide flac, WAV: 44.1/48/96 kHz, 16/24-bit and BWF (Broadcast Wave Format): 44.1/48/96 kHz, 16/24-bit

Over and above these specifications:

  • my productions have no “boxy” or “echoing” room sound, since my recording space is acoustically treated. 
  • There is no distracting background noise such as hiss, computer fan noise, distant traffic, footsteps, creaks, crackles and rattles, etc.
  • There is no audible noise reduction on my recordings (i.e when the background noise noticeably disappears at the end of each word) and natural breaths are not automatically removed.
  • I pay close attention to frequency equalization, which I customise to each project, the end result being neither too bassy or “boomy” or thin and trebly.
  • I test-listen my finished productions on a variety of devices, in addition to my reference-quality headphones and studio monitors, to ensure consistency, including: small laptop speakers, apple earbuds, mid-range hi-fi speakers and in-car speakers.


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