Audiobook Recording Specifics
The history of audiobooks is rooted in accessibility. Audio publications and publications that synchronize text and audio playback have long been used to assist users with alternative reading needs and preferences. Audiobook recording should include volume and level consistency, the use of optimum recording techniques and equipment, and consistent vocal and room tone (W3C.org).
Many commercial audiobooks are recorded at 320Kbps which is very high for a single vocal. National Network for Equitable Library Service (NNELS) recommends 128-192Kbps for books with stereo effects, and 64-96 kbps for audio with no effects. This results in high quality audio with faster download times and smaller storage.
This is an important accessibility factor, as people that rely on audio for information may not have the storage for so much data, or the time/internet connections for long downloads. Keeping the file size low increases the accessibility of the file, without much compromise to the audio.
These are some of the audio requirements at NNELS for recording audiobooks:
- Include one second of room-tone at the beginning of every section and three seconds of room-tone at the end.
- Room-tone: Noise floor is at -60db maximum, which is close to silence.
- Level: The recording should measure between -23db and -18db RMS (average) with peak values no higher than -3db.
- File type: If the audiobook is using stereo effects, it should be exported as balanced stereo MP3s at 128-192 kbps. If the audiobook is only voice with no effects, it should be exported as mono MP3s at 64-96 kbps.
If images in the book demonstrate what is happening or are too abstract to describe, consider adding music and/or sound effects to a book. This would result in an enhanced experience for most readers.
Consistent volume and levels are crucial to protect the readers hearing and it is important to avoid level fluctuations, which interrupts reading. Volume should remain consistent from chapter to chapter. Use professional recording techniques and equipment to avoid hums, hissing, buzzing, and distortion, which can strain hearing and the nervous system.
Including detailed metadata enhances accessibility by allowing the reader to easily find out key information about the book including the title, author's name, ISBN, and the date it was published. Embedding information in audiobook files also enables playlist compatibility across different devices
Children's audiobooks may require special attention to ensure that the listening experience is as engaging as possible.
Illustrated children's books are unique when it comes to accessibility, and there is no one-size-fits-all way of handling them. The content, style, and format of the book all factor into deciding how to best approach the recording, but here are some basic points to consider:
- If the images are integral to understanding the story, or depict things not mentioned in the text, include image descriptions. It is recommended that the author write the image descriptions, so they match the tone and style of the text.
- Enhanced EPUBs can hold more than one audio track so readers have the option to "Read-along" or "Read-along with image descriptions," thus ensuring a rich reading experience.
- If the images in the book simply demonstrate what is happening, or perhaps are too abstract to describe, consider adding music and/or sound effects to a book to enhance the experience.
Following research and guides published by The National Network for Equitable Library Service (NNELS), BookNet Canada, eBOUND Canada, and CNIB/Beyond Print, and others, this guide is a broad overview that briefly outlines current and developing practices in accessible audiobook publishing. It explores making audiobook content accessible and provides a Quality Assurance Checklist for accessibility. A glossary of terms related to accessible audiobooks is included, as is a list of further resources.