48kHz/24 bit Recordings: Voice Over File Formats Talent Should Send

The professional default is a WAV master recorded at 48kHz, 24-bit, mono. Send that as your final delivery unless a client asks for something else. For auditions, a high-bitrate MP3 is fine and expected. What you should never do is take an MP3 and convert it back into WAV hoping to pass it off as a lossless file. That trick doesn't work, and engineers can tell.

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TL;DR:

• Recording at 48kHz and 24-bit in mono is the industry standard, providing ample headroom for editing and meeting most client specifications.
• Use WAV or AIFF for final masters, especially for broadcast or audiobooks, since they are uncompressed and preserve data integrity.
• Deliver audition files as high-bitrate MP3s (320 kbps) for quick review, but never convert MP3s back into WAV to pass off as lossless.
• Match file formats and specs to the project's purpose: WAV for delivery and editing, MP3 for auditions, and low-sample-rate codecs like u-law for telephony.
• Confirm file naming, quality, and playback before delivery; sending a clear, high-quality WAV master with an MP3 preview helps avoid revisions and delays.

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Table of Contents

• Voice Over File Formats Compared: WAV, MP3, AIFF, and More
• Recording Specs: Sample Rate, Bit Depth, and Channels That Actually Matter
• Matching the Format to the Job: Auditions, Delivery, Streaming, and Audiobooks
• Your Delivery Checklist Before You Hit Send
• How Voicebros Guides Clients and Talent on File Delivery
• Why Bad File Habits Cost More Than a Redo
• Get Your Voice Over Delivered Right the First Time
• Sources
• FAQ

Voice Over File Formats Compared: WAV, MP3, AIFF, and More

Every voice over file format trades something for something else. WAV and AIFF give you uncompressed audio with zero data loss, which is why they're the working standard across broadcast, e-learning, and audiobook production. AIFF is Apple's version of the same idea, functionally identical to WAV for most purposes, though WAV remains more universal across editing software. The Library of Congress lists WAVE as a preferred format for long-term audio preservation, and that recommendation carries weight because archivists care about exactly the same thing voice actors should: not losing information you can't get back.

MP3 sacrifices some of that fidelity to shrink file size, and for most day-to-day communication, that trade is worth it. An MP3 at a suitably high bitrate sounds clean enough for an audition, a quick client review, or an email attachment nobody wants to wait long to download.

Beyond the big three, a few other formats show up depending on where the audio ends up:

• FLAC compresses audio without throwing away any data, useful for archiving large session files or distributing high-quality audio when storage space matters. Xiph covers the format in detail for anyone setting up an archive workflow.
• AAC is the codec behind most streaming platforms and mobile apps, chosen for its balance of small size and decent quality.
• Opus handles low-latency, high-efficiency streaming particularly well, which is why it's become common in web and video conferencing tools, according to Opus codec documentation.
• Broadcast WAVE (BWF) files carry extra metadata, including loudness information, and support broadcast exchange standards that plain WAV files don't touch.

Know which bucket your project falls into before you hit export, because picking wrong wastes a round-trip with the client.

Recording Specs: Sample Rate, Bit Depth, and Channels That Actually Matter

Record at 48kHz, 24-bit, mono, and you'll rarely have to think twice about compatibility. Video and broadcast production standardized on 48kHz years ago, and the extra headroom from 24-bit recording means quieter noise floors and more room to fix levels in post without introducing digital distortion. Voice-over practitioner guidance backs this as the practical default for most projects, and it's the spec most production houses expect without asking.

Statistic to know: ACX's Audio Lab tool checks submitted files against exact metrics: RMS levels, peak levels, bitrate, and noise floor, then flags anything that fails audiobook submission standards. If your session was recorded sloppy, no amount of post-processing fully rescues it.

Some quick rules worth keeping on a sticky note near your mic:

• Record high, deliver to spec: 48kHz/24-bit is your studio setting, but you can always down-convert to 44.1kHz/16-bit if a client specifically requests it.
• Mono is standard for single-voice narration; stereo only makes sense when you're layering multiple voices or adding music beds.
• Watch your peaks. Anything clipping above 0dB is unusable, and ACX rejects submissions that don't meet its loudness and noise-floor thresholds.
• When in doubt on bitrate for an MP3 audition, default to a high bitrate. Nobody complains about a file sounding too clear.

Down-converting from a high-quality master to a smaller spec is safe. Going the other direction, stretching a low-quality recording up to sound "better," accomplishes nothing.

Matching the Format to the Job: Auditions, Delivery, Streaming, and Audiobooks

Different jobs call for different formats, and mismatching them either wastes bandwidth or fails a technical requirement outright.

1. Auditions. Speed matters more than fidelity here. A 320 kbps MP3 lets you send a quick take without anyone waiting on a massive download, and it's the accepted norm across casting platforms.
2. Final delivery and mixing. This is WAV territory, often as Broadcast WAVE when the client needs embedded metadata or loudness information for their broadcast pipeline. Editors want the full, uncompressed signal to work with.
3. Audiobooks. Platforms like ACX enforce specific technical requirements around sample rate, bit depth, loudness, and file format, and non-compliant files get bounced back before they ever reach a listener. WAV is typically the expected submission format, checked against those published specs.
4. IVR and telephony systems. These run on older, narrower infrastructure, and engineers frequently ask for low-sample-rate codecs like 8kHz u-law rather than anything close to studio quality. Always get the spec sheet before recording, not after.
5. Web and social media. AAC or Opus wins here because streaming platforms prioritize fast loading and small file sizes over raw fidelity, and most viewers are listening through phone speakers anyway.

The pattern across all five: fidelity requirements drop as the audio moves further from the editing room and closer to the listener's ear. Match the format to where the file is actually going, not to what feels the most "professional" in the abstract.

Your Delivery Checklist Before You Hit Send

A rushed delivery is how good voice actors end up looking unprofessional. Before you send anything, run through this:

• Double-check format, sample rate, bit depth, and channel count against what the client actually asked for.
• Name your files clearly and consistently: something like ClientName_ProjectName_Take02.wav, no spaces, no version confusion.
• Listen to the entire file top to bottom, not just the first ten seconds. Clicks, mouth noise, and wrong takes hide in the middle just as often as at the start.
• Pick a transfer method that matches the file size. Cloud links work for large WAV masters; email attachments are fine for MP3 previews.
• Confirm the client actually received the file and that it plays correctly on their end before you consider the job closed.

Pro Tip: Send both a WAV master and an MP3 preview in the same delivery. Editors get the full-quality file they need, and the client gets something they can play instantly on a phone without downloading anything.

How Voicebros Guides Clients and Talent on File Delivery

Across thousands of projects on the Voicebros platform, the pattern holds steady: talent who keep a WAV master on hand and send an MP3 preview alongside it get fewer revision requests and faster approvals. Consistent file naming and basic metadata (project name, take number, date) cut down on the back-and-forth that eats up turnaround time.

Voicebros structures its voice over services around this exact expectation, so clients booking commercial, e-learning, or audiobook work know what a properly delivered file looks like before the project even starts.

Why Bad File Habits Cost More Than a Redo

The mistake I see repeated most often isn't a bad performance. It's someone converting an MP3 back into WAV and calling it a final master, hoping nobody notices the compression artifacts baked into the file. Engineers notice. Naming files clearly and testing playback before sending takes five extra minutes and saves a client relationship. When a spec sheet is unclear, ask. Guessing costs more than the question ever does.

— Onur

Get Your Voice Over Delivered Right the First Time

There are platforms designed to simplify finding voice actors who understand broadcast specs. Quality platforms often feature vetted artists who work within standard delivery formats, reducing the need to explain file format differences.

Filtering by language, accent, category, and budget helps find voice actors suited to project specifications, whether for Broadcast WAVE files or audiobook formats. Some platforms offer live demo comparisons before commitment, allowing clients to hear voices and quality in advance. Browse professional voice artists ready to deliver to spec, or check the platform fee structure to see exactly what a project costs before you book.

Sources

For anyone who wants to go straight to the primary references: the Library of Congress's WAVE format page and its Broadcast WAVE Version 2 documentation cover archival and broadcast standards in detail. FLAC's documentation explains lossless compression for archiving, and ACX's Audio Lab lets you check a file against real audiobook submission metrics before you upload anything.

• WAVE Audio File Format — Library of Congress
• ACX Audio Lab — Audible
• Xiph

FAQ

What Is the Best File Format for Audiobooks?

WAV is the standard submission format for audiobook platforms, checked against specific sample rate, bit depth, and loudness requirements. ACX's Audio Lab analyzes files against these exact metrics before acceptance, so running your file through it first catches problems before submission.

What Is the Best File Format for Voice Recording?

Record in WAV at 48kHz and 24-bit in mono for the cleanest working master with the most editing headroom. This spec is the practical industry default recommended across voice-over production guidance.

What Are the Three Main Types of Audio File Formats?

Audio files generally fall into three categories: uncompressed (WAV, AIFF), lossless compressed (FLAC), and lossy compressed (MP3, AAC, Opus). Uncompressed formats preserve every bit of original data, lossless compression shrinks size without losing quality, and lossy compression sacrifices some fidelity for much smaller files.

Are Voice Over Files MP3 or MP4?

Voice over audio is almost always delivered as MP3, WAV, or a similar audio-only format, not MP4, which is a video container that can hold audio but isn't built for pure audio delivery. If you receive an MP4 file for a voice-over project, the audio track should typically be extracted and delivered as a standard audio file instead.

Should I Ever Convert an MP3 Back Into WAV?

No. Converting a lossy MP3 into WAV doesn't restore any of the data lost during compression, and the resulting artifacts are recognizable to anyone editing professionally. Always keep your original WAV master file instead of trying to reverse-engineer quality from a compressed copy.

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