Why is my video's audio so quiet — and can this clip be saved?

Nine times out of ten it's one of five things: something was covering the mic, you were too far from whatever you were recording, the phone's automatic gain control ducked the level after a loud moment, wind noise suppression clamped the whole track, or the room was quieter than your ears told you. Your ears adapt. The mic doesn't. A conversation that felt perfectly normal in the room can land 25 dB below full scale in the file, and that plays back as a whisper.

Most of it is fixable after the fact. Some of it isn't, and it's worth knowing which is which before you spend an hour on a recording that can't be saved.

First, find out how quiet it actually is

"Too quiet" is a feeling. A number is more useful. Drop the file into the video volume booster and press Smart Boost. It scans every sample and reports the sample peak in dBFS, the RMS level, the integrated loudness in LUFS, and how much headroom is sitting unused above the loudest moment. The loudness figure is a real ITU-R BS.1770-4 measurement: K-weighting filters, 400 ms blocks with 75 % overlap, an absolute gate at -70 LUFS and a relative gate at -10 LU. Worth being precise about one thing: it's sample peak, not true peak (dBTP), so it doesn't predict inter-sample overs that appear after you re-encode.

Those numbers tell you which problem you have.

Headroom is the honest version of "how much louder can this get". If Smart Boost reports 18 dB of headroom, that's roughly 7.9 times the original amplitude before the loudest sample touches full scale, and the button hands you the exact percentage that gets there with 1 dB of margin and zero clipped samples. The slider stops at 500 %, which is about +14 dB. For a really deep hole you can export the boosted WAV, load that file back in, and boost again.

Something was over the mic

This is the most common cause and the most annoying, because it's invisible while you record. On an iPhone the mics sit at the bottom edge, near the rear camera, and in the earpiece. Android layouts vary, but the pattern is the same: at least one mic sits somewhere your hand naturally lands when you hold the phone in landscape.

A finger doesn't have to fully block a port to cost you level. Partial coverage plus a thick case is enough to drop 10 to 15 dB and dull the top end, which is why these recordings sound both quiet and like they were made through a pillow. Pocket lint packed into the mic mesh does the same thing permanently until you clean it out. A dry soft brush, never a pin.

The level is recoverable. The muffling is not. Boost a covered-mic recording and you get a loud muffled recording. You can claw back some intelligibility with the Voice preset in the 5-band equalizer, which cuts 60 Hz by 4 dB and 230 Hz by 2 dB while lifting 910 Hz by 3 dB, 3 kHz by 5 dB and 14 kHz by 2 dB. It can't restore treble that never made it into the file.

Distance costs 6 dB every time you double it

Sound from a point source spreads over an expanding sphere, so intensity falls with the square of distance. In practice: double the distance from the source, lose about 6 dB. That's the biggest lever in any recording and it's the one people ignore.

• Phone at arm's length, roughly 60 cm from a talker: healthy level.
• Phone on the table 1.2 m away: about 6 dB quieter.
• Phone at the back of a classroom, 5 m from the lecturer: around 18 dB down from arm's length.

Eighteen dB is an enormous gap. Gain can put most of it back, but here's the catch most pages skip.

Distance also wrecks the ratio of direct sound to room reflections. Close up, you mostly capture the voice. Far away, you capture the voice plus every bounce off the walls, which is why distant recordings stay washy even after the level is fixed.

Automatic gain control pulling the level down

Phones run AGC on the mic input so a shouted voice and a quiet one both land in a usable range. It watches the incoming level and adjusts gain on the fly. When something loud happens, a chair scraping or a laugh or a door, the AGC pulls gain down fast to protect against clipping, then eases it back up over the next several seconds.

If your subject speaks quietly right after a loud event, that speech is recorded at the reduced gain. Play it back and it sounds like someone turned you down. That's what happened.

AGC damage is partly fixable. If the level is uniformly low, a single boost fixes it. If it pumps up and down across the recording, one static setting can't chase it. The realistic approach is to boost to the level the quiet passages need and let the soft limiter catch the loud sections. It's a tanh-knee waveshaper: transparent below 0.7 of full scale, asymptotically approaching full scale above it. A ceiling, not a compressor with attack and release, so it never breathes or pumps. It just refuses to let anything past the top.

Wind suppression and the wrong mic mode

Record outdoors and the phone's wind-noise reduction engages. It's a high-pass filter plus level reduction that kicks in when the DSP detects the low rumble of air hitting the mic. It works. It also clamps everything else while it's active, so a windy day can leave you 10 dB quieter than the same shot indoors, with the low end scooped out.

The other version: you recorded in a mode that used a different mic than you expected. Front camera and rear camera can route to different capsules. Some phones tie directional or "audio zoom" processing to the camera's zoom level, attenuating anything off-axis. Zoom in on someone across a park and the phone may deliberately suppress the ambience, and if it guessed wrong about direction, it suppressed your subject too.

Both are gain problems in the file, so both respond to boosting. Neither is reversible in terms of tone. If the wind filter removed 80 Hz, no amount of low shelf brings it back, though a little of the 120 Hz low shelf can make what survived feel fuller.

The fix: measure, boost, limit, shape

Everything above leads to the same four steps, in this order.

1. Measure. Load the file and run Smart Boost. Note the headroom figure. That's your free gain, and everything up to it costs you nothing but a louder noise floor.
2. Boost to the suggested number. Click it. Zero clipped samples, 1 dB of margin. If Smart Boost says 340 %, that's about 10.6 dB of real gain.
3. Go past it with the limiter on. Speech usually needs more than the peak allows, because one stray bang is holding the peak hostage. Push further and watch the live clip warning, which names the exact percentage of samples that would run past full scale. The limiter is on by default and rounds those off instead of squaring them into distortion.
4. Shape for voice. Open the equalizer and try the Voice preset (-4, -2, +3, +5, +2 dB at 60, 230, 910, 3000 and 14000 Hz, five peaking filters at Q = 1.0). Cutting the bottom removes rumble that eats headroom without carrying any words. The lift at 3 kHz is where consonants live. Use the level-matched A/B button to judge it: it trims the processed side back to the original's peak, so you hear the tone change instead of just "louder", which is the only fair way to tell whether an EQ move helped.

Be clear on what comes out the other end. The video tool boosts the audio, plays the video back boosted, and exports the boosted audio as a WAV (16-bit, 24-bit or 32-bit float). WAV only, no MP3. It does not re-encode the video, so you get a clean loud audio track to drop back alongside the original clip in whatever editor you already use. Occasionally a browser will play a video it can't decode the audio track from separately. Playback is still boosted in that case, but the export can't run, and the iPhone app or the Android app can export from video files directly. Everything on the site runs in your browser with no upload, no account and no length limit past what your device's memory holds. Turn Wi-Fi off after the page loads and it keeps working.

Getting a louder recording next time

Prevention beats repair, because none of this adds signal that isn't there.

• Halve the distance. That's +6 dB for free, better than any plugin.
• Check your grip before you hit record. Know where your phone's mics are and keep fingers off them.
• Get out of the wind, or put a body between the wind and the phone. A jacket held up as a windbreak helps.
• Avoid loud noises at the start of a take, so AGC isn't already pulling down when the important part begins.
• For anything that matters, use a wired lav clipped about 20 cm from the mouth. A cheap lav beats an expensive phone held across the room, every time.

If the recording you're rescuing is a voice memo rather than video, the same measure-then-boost logic applies and there's a walkthrough for quiet voice memos. For the full step-by-step on video, see making a video louder, and for how far you can push before things start sounding bad, boosting without distortion covers the limits.