FIX BAD FILM AUDIO WITH JUST AN IPHONE (+ FREE TOOLS)

If you've shot a film and now you realize the audio sounds terrible, then this is for you. Having good audio is crucial because even if your image looks amazing, bad audio will instantly make your film feel amateurish. In the words of Gareth Edwards:

“You forgive a bad image if you can clearly hear the sound well, but you don't forgive a great image if the sound is terrible.”

Now here's the good news! I'm going to walk you through how you can rebuild your audio to a pro cinematic level using just your iPhone and free software. This will work whether you've already filmed something with bad sound, or even if you're just looking for a DIY way of getting pro audio on a budget. So now let's dive in.

✅ What You Need:

• iPhone or any smartphone with a mic

• Laptop + headphones

• Free audio software: Audacity

• Step 1: Take Stock of Every Sound

  Go through each scene of your film (for which you want to repair the audio) and list out all sounds you hear in each scene. List these into 3 categories:

• Dialogue – Transcribe every line as it’s spoken.

• Onscreen Sounds – Footsteps, keys, clothes, etc.

• Ambient Sounds – These are the background sounds. So wind, trees, birds, etc

• Step 2: Rerecord Dialogue (ADR)

• It’s now time to re-record  the dialog in a process also known as ADR (Automated Dialog Replacement). There are a few best practices to make sure that you get the best quality audio with your iPhone:

  • Record in a quiet space – Closets work great.

  • Actors should wear headphones – To avoid audio bleed.

  • Actors should watch the scene while recording – to help match performance timing + emotion.

  • Record all lines in one single audio file per actor - this will save you time in the edit later.

  • Aim to get 5 good takes per line

  • Start each audio file with 10 seconds of silence – You’ll need this for audio cleanup later.

  💡 Pro Tip: Can’t meet in person? Send actors the instructions, and they can record at home.

• Step 3: Rerecord Onscreen Sounds (Foley)

Now we’re going to re-record all of the onscreen sounds in a process also known as Foley. We’re going to do so using our iPhone - and ideally - we're going to record each sound in a quiet environment. 

Even if your scene takes place outdoors, recording the foley indoors will help you get higher quality audio, especially when recording with an iphone! 

Here are the best-practices for foley recording:

• Use a quiet room, even if the scene was outdoors - as just discussed. 

• Record sounds one by one — each in its own audio file (unlike ADR).

• Include 10 seconds of silence before each sound (like ADR).

💡 Pro Tip: If you can’t record a sound CLEANLY with your iphone - download copyright-free sound effects from freesound.org.

• Step 4: Clean the Audio (Using Audacity)

• Now we’re going to go through all of our ADR and Foley files, and make sure that we remove any unwanted background noise. To do that we're going to use a free software called audacity.

  • Download Audacity: audacityteam.org

  • Once you have Audacity downloaded and open on your computer - import each audio file (ADR + Foley).

  • Go through each audio file and follow the below steps to remove unwanted background noise:

  • Highlight the 10 seconds of silence at the top of each audio file then go to  → Effect > Noise Reduction > Get Noise Profile.

  • Select the full track and do → Effect > Noise Reduction again.

  • Adjust:

  • Noise Reduction = how much to remove.

  • Keep it low to avoid hurting voice quality.

  • Play it back. If it sounds clean, you’re good to go!
    

• Step 5: Replace audio in Your Edit

Once all audio is cleaned up, it’s time to all all ADR and Foley files into the edit - to replace the original bad audio.

• Go back to your timeline.

• Drop in your clean ADR and Foley to sync up with the on-screen action. 

• For ADR: you may not be able to find an exact 1-1 performance match, and that’s okay. What you can do, is combine different bits from different takes and cut them together to match the on-screen performance. 

• For Foley: if a foley recording doesn’t sync up neatly with the on-screen action, then either try re-recording the foley, or downloading an option from freesound.or - they have TONS to choose from, and you’ll likely find a file that matches your action. 

• For Background noise: Download all background noises from freesound.org - these will be higher quality than recording them with your phone, and you can find sounds that match the texture of your scene! 

If you have any music you want to add to the scene, be sure to include it. Great copyright free music resources include: Artlist.io and Epidemic Sound 

• Step 6: Final Mix

  So now we've put everything together and we can move on to the final step, which is the final mix. 

  Whenever you're mixing a scene, there is a certain hierarchy of priorities that you want to follow:

  • 1st (Loudest): Dialog - dialog should be heard above all else. None of the sounds can overpower the dialog, unless of course, that is a very intentional stylistic choice.

  • 2nd: Foley 

  • 3rd: Ambient

  • 4th: Music 

  Certain scenes will call for different mixing priorities, but I would say whenever in doubt, follow this protocol and you will be good to go!

• final thoughts

  That’s how you take terrible audio and turn it into something that sounds cinematic — all from home, and a budget. I very often hear the term “fix it in post” when it comes to audio, and I just want to say that no matter how powerful AI plugins are getting today to repair bad audio - you will never be able to transform bad audio into great audio. One of my favorite sayings is “garbage in, garbage out.”

  But if you’re in a situation where you realize that your audio doesn’t sound clean - this is the right way to “fix it in post.” 

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