How to bleep out phone numbers in audio recordings — free
- Step 1Open the redactor and drop your recording — Drop the call or voicemail into the redactor. Audio input is accepted (MP3, WAV, FLAC, M4A, OGG, Opus); Pro-tier covers 200 MB and 120 minutes per file — enough for most call recordings.
- Step 2Let the file decode in your browser — The tool decodes the audio locally to read its duration. Nothing is uploaded — FFmpeg 8.1 runs as WebAssembly inside the page, so the recording never leaves your device. The decoded duration becomes the upper bound for every range you add.
- Step 3Add a redaction range — Click Add range. A row appears with Start and End number inputs (in seconds). A new range defaults to 0 s to 1 s; type the real start and end of the segment you want silenced.
- Step 4Mark every segment that needs silencing — Find where each number is read and add a range for it. Numbers spoken with pauses run longer than you expect (a 16-digit card can be 6–8 s), so set the End past the final digit and pad both ends. There is no auto-detector — you locate the numbers.
- Step 5Process the file — Run the tool. For each range it applies
volume=0gated tobetween(t, start, end), so the audio inside every marked range becomes pure silence. The rest of the timeline is untouched and the file is re-encoded to the output format. - Step 6Download and verify — Listen to the
-redactedoutput over each number's window and confirm every digit is silent, including the last one. If a trailing digit survived, widen the End and reprocess from the original recording.
What the redactor actually does
Every row verified against the browser processor and the range UI. The tool mutes — it does not bleep, beep, or insert noise.
| Behaviour | Implementation | What it means for you |
|---|---|---|
| Redaction method | Volume set to 0 (full silence) inside each marked range via the FFmpeg volume filter with an enable='between(t,start,end)' gate | No tone, beep, or noise is inserted — the range goes silent |
| Marking | Manual only — you add ranges with Add range and type Start and End in seconds | There is no auto-detection, transcription, or phone-number finder in the tool |
| Time granularity | Start/End inputs step in 0.1 s (100 ms) increments | Type a finer value directly if your browser allows; the filter uses your exact number |
| Range bounds | Each input is clamped to min 0 and max = the file's decoded duration | You cannot mark a range past the end of the file |
| Output format | Defaults to the input file's extension and is re-encoded through FFmpeg | Lossy inputs (MP3/M4A/OGG/Opus) are re-compressed; WAV/FLAC stay lossless |
| Filename | Original name with a -redacted suffix | e.g. interview.mp3 becomes interview-redacted.mp3 |
| Empty input guard | Throws Add at least one redaction range if no range is set | At least one Start/End pair is required before processing |
Input and output formats
Output is re-encoded through FFmpeg 8.1 (WebAssembly). The output extension follows the input by default; the encoder is chosen from that extension.
| Format | Output encoder used | Lossy on re-encode? |
|---|---|---|
| MP3 | libmp3lame | Yes — re-compressed (one extra lossy generation) |
| WAV | pcm_s16le | No — lossless PCM |
| FLAC | flac | No — lossless |
| M4A / AAC | aac | Yes — re-compressed |
| OGG (Vorbis) | libvorbis | Yes — re-compressed |
| Opus | libopus | Yes — re-compressed |
Audio tier limits that apply to redaction jobs
PII redaction runs inside the audio tool family, so the audio family limits apply. Numbers are per the live tier table; durationMin is a per-file duration cap that is separate from the file-size cap.
| Tier | Max file size | Max duration / file | Files per job |
|---|---|---|---|
| Free | 50 MB | 30 min | 1 |
| Pro | 200 MB | 120 min | 10 |
| Pro-media | 100 GB | Unlimited | 100 |
| Developer | 100 GB | Unlimited | Unlimited |
Cookbook
Recipes for muting spoken numbers. Pad ranges — slowly-read numbers are longer than they sound. Times are seconds.
Mute a credit card number read on a support call
A caller reads a 16-digit card number with pauses between groups, taking about 7 seconds. Box the whole sequence with margin.
Range: Start: 184.0 End: 191.5 (~7.5 s window)
All 16 digits + the pauses are silenced. Pad the End so the
final group ('...spoken slowly') is fully covered.
Output: support-call-redacted.mp3Bleep a callback phone number on a voicemail
A voicemail ends with a 10-digit callback number. Mute just that, keeping the rest of the message.
Range: Start: 22.0 End: 27.0 (10 digits, read once) The number is silent; the spoken message before it is intact.
Redact a PIN stated mid-meeting
A short PIN (4 digits) is said once at 5:03. A tight range plus a small pad on each side does it.
Range: Start: 302.6 End: 304.4 Short, so a ~1.8 s window covers it. Pad slightly so the first and last digit aren't clipped.
Two card numbers in one call
A caller corrects themselves and reads a second card number later. Add a range for each — order doesn't matter.
Add range 1 -> Start: 95.0 End: 102.0 (first card) Add range 2 -> Start: 140.0 End: 147.5 (corrected card) Both are silenced in the same pass.
Widen a range when the last digit survived
First pass left the final digit faintly audible because the speaker trailed off. Extend the End and re-run from the original.
Before: Start: 184.0 End: 190.0 -> last digit leaks After: Start: 184.0 End: 191.8 -> fully muted Reprocess from the original call - non-destructive.
Edge cases and what actually happens
Last digit of a number still audible
ExpectedNumbers read with pauses trail off; if the End landed mid-sequence, the final digit can survive. Extend the End by 0.5–1 s and reprocess. The classic cause of an incompletely redacted number.
No range added
RejectedProcessing with no ranges throws Add at least one redaction range. Add a Start/End window over each number first.
Range too short for a slowly-read card number
ExpectedA 16-digit card spoken in groups can take 6–8 s. A 3-second range will only catch part of it. Time the full utterance and pad the End.
Number repeated for confirmation
Add another rangeIf the agent reads the number back to confirm, that repeat is a second utterance — add a separate range for it, or it stays audible.
Inverted range (End before Start)
By designAn empty window silences nothing and the number stays audible. Check that End is greater than Start.
Expecting an audible bleep over the number
By designDespite the page name, redacted spans are silent — there is no inserted beep tone. The digits are muted, which equally prevents recovery.
Overlapping ranges for adjacent numbers
SupportedTwo numbers read close together can be covered by overlapping ranges; the union is silenced with no error.
Phone number also written in the file's tags/name
Not handled hereMuting the audio does not remove a number stored in ID3 tags or the filename. Clear those with id3-editor and rename the file.
Call longer than the tier duration cap
RejectedDuration is capped per tier (Free 30 min, Pro 120 min, higher unlimited) separately from file size — a long recorded line may need Pro or above.
Frequently asked questions
Does the tool insert a beep, tone, or white noise over the redacted part?
No. The redactor sets the volume to 0 inside each range, so the segment becomes full silence. There is no beep tone, 1 kHz tone, or white-noise option in the tool — it is a mute, not a bleep. If you specifically need an audible censor beep for broadcast style, you would have to add it in a separate audio editor; this tool's output is silent across the marked ranges.
How precise can the redaction boundaries be?
The Start and End inputs step in 0.1 s (100 ms) increments, and the underlying between(t, start, end) filter uses the exact number you type. For most speech that 100 ms granularity is enough to catch a spoken digit or word; pad each range by a few hundred milliseconds on both sides so the leading consonant or trailing syllable is fully covered.
Can the silenced audio be recovered from the output file?
No. The samples inside each range are replaced with silence before encoding, so the original audio in those spans is not present in the output file — there is nothing to un-mute. Keep your original recording in a secure location if you ever need the un-redacted version; the redacted file cannot be reversed back to it.
Can it automatically find names, numbers, or card details?
No. Marking is manual only — you add ranges and type the Start and End seconds yourself. There is no speech-to-text, entity recognition, or phone-number detector built in. Play the recording, note the timestamps where sensitive content is spoken, and enter those ranges. This keeps everything in the browser with zero upload, but it does mean you (or a reviewer) decide what gets silenced.
How many separate sections can I redact in one pass?
As many as you need — click Add range for each section. Every range is applied in the same processing pass as its own volume=0 gate, so a call with ten scattered account numbers is one job, not ten. There is no fixed cap on range count; the practical limits are the file-size and duration caps for your tier.
Is my recording uploaded to a server?
No. All processing is 100% in your browser using FFmpeg 8.1 compiled to WebAssembly. The audio is decoded and redacted locally and never transmitted, which is what makes the tool suitable for sensitive recordings. You can disconnect from the network after the page loads and redaction still works.
What happens if two ranges overlap?
Overlapping ranges are fine — each is an independent volume=0 gate, so the union of all ranges is silenced. If range A is 10–15 s and range B is 14–20 s, the audio from 10–20 s ends up silent. There is no error for overlap; it simply mutes everything any range covers.
Will the redacted file be the same length as the original?
Yes. Muting a range does not remove time — the silenced spans stay in place, so the total duration is unchanged. This is intentional: it keeps every later timestamp aligned with your notes, transcript, or video. If you actually want the file shorter, trim or strip silence instead.
Does redacting also remove names or numbers stored in the file's metadata?
No. This tool silences audio samples within the ranges you mark; it does not touch ID3 tags, comments, or cover art embedded in the file. If a phone number or name is sitting in the title/artist/comment fields, edit those separately with id3-editor, and consider whether the filename itself leaks anything.
Does the output stay in the same format as my input?
By default yes — the output extension follows the input file's extension and is re-encoded with the matching encoder (MP3 to libmp3lame, WAV to pcm_s16le, FLAC to flac, M4A to aac, OGG to libvorbis, Opus to libopus). So an MP3 in gives an MP3 out, named with a -redacted suffix.
I marked the wrong segment — how do I fix it?
Each range row has a trash/remove control. Delete the wrong range, add a corrected one, and reprocess. Because the tool is non-destructive to your source file (it produces a new -redacted output), you can re-run as many times as you like from the same original until the boundaries are right.
Should I just trim out the sensitive part instead?
Trimming with audio-trimmer physically cuts a span, which shortens the file and shifts every later timestamp — bad if you have a synced transcript, captions, or chapter markers. Redacting mutes in place and keeps the timeline intact. Trim when the sensitive part is at the very start/end and length doesn't matter; redact when it is mid-recording or timing must be preserved.
Privacy first
Every JAD Audio tool runs entirely in your browser via FFmpeg (WebAssembly) and RNNoise. Your audio files never leave your device — verified by zero outbound network requests during processing.