Your clips have sound. Your film doesn't.
Effct sound-designs the whole cut. Ambience, effects, whooshes and impacts, in sync, each on its own clip.
Free: the first 30 seconds of one video, previewed in the editor. Exporting needs a paid plan.
Updated
Effct is sound design for AI video. Stitch your Veo, Kling, Seedance or Runway clips into one cut and upload it. Effct places ambience, sound effects, whooshes and impacts across the whole film, in sync with the picture. Every sound lands on its own clip, so you can swap, move or remove it, then export the mix, stems or an AAF.
Use it as is. Or make it yours.
Why AI clips don't sound like one film
Most video models now make sound with the picture, but each generation covers one short clip, and every clip gets its own room. Stitch them together and the ambience changes at every cut.
| Tool | Sound with the picture | Length per generation | Separate sound files | Source |
|---|---|---|---|---|
| Veo 3.1 (Google) | Yes, always on | 4, 6 or 8 seconds; extend in 7-second steps | Not stated | Gemini API: Veo |
| Kling 3.0 | Yes, native audio | Up to 15 seconds | Not stated | Kling 3.0 |
| Kling 4.0 | Not stated | 3 to 30 seconds; extend to 2 minutes | Not stated | Kling 4.0 |
| Seedance 2.0 (ByteDance) | Yes, made together with the picture | Up to 15 seconds, multi-shot | Describes multi-track output for music, ambience and voices; separate files not stated | ByteDance Seed |
| Gen-4.5 | Not stated | Not stated | Not stated | Runway API models |
| Several models, among them Kling, Seedance and Veo | Depends on the model you pick; Higgsfield Audio is for speech | Depends on the model | Not stated | Higgsfield, Higgsfield Audio |
Sound for Veo videos
Veo 3.1 makes each clip with its own sound, always on, in clips of 4, 6 or 8 seconds; each extension adds 7 more. Cut ten clips together and you hear ten rooms. Export the cut, upload it to Effct, and it designs the sound across all the shots: ambience for each place, effects on the action, whooshes and impacts on the cuts. Every sound is its own clip, so you can swap or remove it.
Sound for Kling videos
Kling 3.0 clips run up to 15 seconds with native audio, and Kling 4.0 makes 3 to 30 seconds a pass. Kling's own Video to Audio adds sound effects to a silent clip, and Kling suggests a separate editor for the mix. That works clip by clip. Effct works on the finished cut, so the sound follows your edit, and every sound comes back as its own clip.
Source: Kling: add sound to AI video
Sound for Seedance videos
Seedance 2.0 makes multi-shot clips of up to 15 seconds, with sound made together with the picture. A longer film still means stitching several clips, each with its own mix. Upload the stitched film and Effct gives it one sound design across every shot, with WAV stems on Creator and an AAF on Pro for the final mix in your editor.
Sound for Runway videos
Runway's model list doesn't say whether Gen-4.5 clips come with sound, and it also offers Veo 3.1, which does. Either way, a film made in Runway is many short shots. Cut them together, upload the cut, and Effct designs the sound for the whole film: ambience, effects, whooshes and impacts, each on its own clip you can change.
Sound for Higgsfield videos
Higgsfield runs several video models, among them Kling, Seedance and Veo, so your shots may arrive with different kinds of sound, or none. Its own Higgsfield Audio is for speech. Whatever made the shots, export the cut and Effct designs one sound across it, every sound on its own clip.
How to add sound design to an AI film
Export the cut
Export your stitched cut as one video: MP4, MOV, AVI, MKV or WEBM, up to 5 GB. Each project holds up to 20 minutes of video; longer videos are split.
Upload it to Effct
Upload the video. On a paid plan, choose whether to keep your clips' own sound in the mix.
Get a layered timeline
Effct places ambience, actions and design sounds on a timeline, in sync with the picture, usually in minutes.
Make it yours
Swap, move, trim or remove any sound, or add one by describing it.
Export
Export a QuickTime with the mix on any paid plan, WAV stems on Creator and up, or an AAF on Pro and up. Or work in Premiere Pro with the Effct panel.
QuickTime with the mix on every paid plan. WAV stems from Creator ($29). AAF from Pro ($49).
Frequently asked questions
How do I add sound effects to an AI video?
Stitch your clips into one cut, upload it to Effct, and it places ambience, sound effects, whooshes and impacts across the whole video, in sync. Each sound is its own clip you can change. Export on any paid plan.
Which AI video tools does Effct work with?
Any of them. Effct works from the exported video file, so it doesn't matter whether the shots came from Veo, Kling, Seedance, Runway, Higgsfield or a mix.
Will Effct replace my clips' own audio?
Your choice, on a paid plan: keep your clips' own sound in the mix under Effct's sound design, or leave it out.
What does the free trial include?
Free: the first 30 seconds of one video, previewed in the editor. Exporting needs a paid plan. The trial places Design and Ambience sounds; footsteps and other action sounds need a paid plan.
How long can my film be?
Up to 20 minutes per project. A longer video is split into projects of up to 20 minutes each.
Can I get stems for my editor?
Yes. Creator and up exports WAV stems, one per sound category (48 kHz, 24-bit). Pro and up adds an AAF with linked WAV files for your editor or DAW.
Read more
Free: the first 30 seconds of one video, previewed in the editor. Exporting needs a paid plan.