AI Voice Dubbing Online
Translate and re-voice your video audio into English, Spanish, German, French, Portuguese, Japanese, or Arabic. Whisper + Opus-MT + Piper TTS + DSP timbre matching — entirely in your browser.
Upload a file · Boost, EQ, export · 100% in your browser
Professional voice dubbing has traditionally required a translation agency, voice actors, a recording studio, and weeks of turnaround time. Even with the recent wave of AI dubbing tools, the typical workflow involves uploading your video to a cloud service, waiting for processing, and paying $50-150 per month for usage-based pricing. These services send your audio to remote servers for transcription, translation, and synthesis — raising privacy concerns for creators working with branded content, unreleased material, or content under NDA.
Hearably Studio's AI Voice Dubbing tool takes a radically different approach: the entire dubbing pipeline runs locally in your browser. There is no cloud upload, no server processing, no usage limit, and no per-minute billing. The pipeline consists of four stages: Whisper transcribes the original speech, Opus-MT translates the text into the target language, Piper TTS synthesizes speech in the target language, and a DSP timbre matcher stamps the original speaker's vocal characteristics onto the synthesized voice.
The supported languages at launch are English, Spanish, German, French, Portuguese, Japanese, and Arabic — covering over 3 billion native speakers and the top markets for content localization. Each language pair requires a translation model (50-100MB) and a TTS voice (approximately 60MB), both downloaded once and cached in the browser. After the initial download, the tool works fully offline.
What makes Hearably's approach unique is the timbre matching stage. Most AI dubbing tools produce output that sounds like a generic TTS voice — clearly synthetic and nothing like the original speaker. Hearably's timbre matcher uses DSP math (not a 2GB neural voice cloning model) to transfer the original speaker's vocal characteristics to the TTS output. The algorithm extracts the speaker's pitch contour via autocorrelation and their spectral envelope via FFT analysis, then applies pitch-shifting and spectral stamping to the TTS waveform. The result is a dubbed voice that retains the tonal quality, pitch range, and formant structure of the original — not a perfect clone, but dramatically more natural than raw TTS.
The complete pipeline is designed for content creators who need to localize their videos for global audiences: YouTube creators expanding to Spanish or Portuguese markets, course instructors making material accessible in multiple languages, podcast producers creating multilingual versions, and businesses dubbing training and marketing content. At Hearably Pro's price of EUR 9.99/month (with unlimited dubbing included), it is a fraction of what competing cloud services charge per minute of processed audio.
The Four-Stage AI Dubbing Pipeline
Hearably's voice dubbing pipeline runs four models sequentially in Web Workers, keeping the main browser thread responsive throughout.
Stage 1 — Whisper Transcription: The video's audio track is extracted and fed to Whisper (base model, 74MB) running via ONNX Runtime in WebAssembly. Whisper produces timestamped text segments with word-level alignment. The language parameter is omitted to allow Whisper's auto-detection, which eliminates errors from manual language misidentification.
Stage 2 — Opus-MT Translation: Each text segment is translated to the target language using Helsinki-NLP's Opus-MT models via the @huggingface/transformers library. Models are 50-100MB per language pair (e.g., en-es, en-de, en-ja) and are cached in the browser after first download. Translation preserves segment boundaries so timing can be maintained.
Stage 3 — Piper TTS Synthesis: Translated text segments are synthesized into audio using Piper TTS running in WASM. Each language has a high-quality neural voice (approximately 60MB). The output is raw PCM audio aligned to the original segment timestamps. Piper produces natural-sounding speech with proper prosody for each target language.
Stage 4 — DSP Timbre Matching: This stage transfers the original speaker's vocal characteristics to the TTS output using pure DSP math. First, the original speech pitch is extracted via autocorrelation on short overlapping windows. The TTS output is pitch-shifted to match using a phase vocoder. Then, the original speech's spectral envelope is extracted via FFT, and the envelope is "stamped" onto the TTS output's FFT magnitudes while preserving the TTS phase information. The result is a voice that has the target language's words and prosody but the original speaker's pitch range and tonal quality. This approach requires zero additional model downloads — it uses the same FFT and DSP primitives that power Hearably's EQ and compressor.
How to get the best audio on AI Voice Dubbing Online
Start with English to Spanish for the largest audience reach
Spanish is the second most spoken language globally with 550+ million speakers. Dubbing English content to Spanish opens the massive Latin American and Spanish markets. The en-es Opus-MT model is one of the highest quality pairs available.
Download language models once, use offline forever
Each language pair requires a one-time download of the translation model (50-100MB) and TTS voice (60MB). After caching, the entire pipeline works offline. Ideal for creators on unreliable internet connections or those processing content during travel.
Process segments individually for best quality
The dubbing pipeline works on timestamped segments. For best results, ensure the original audio has clear speech with minimal overlap. If Whisper misaligns a segment, you can edit the transcription before translation to correct errors before they propagate through the pipeline.
Timbre matching works best with clear original speech
The pitch and spectral envelope extraction rely on clean speech input. If the original audio has heavy background music or noise, the timbre matching may be less accurate. For best results, process videos where speech is the dominant audio element.
Combine with subtitle export for dual accessibility
The Whisper transcription and Opus-MT translation produce text that can be exported as SRT subtitles alongside the dubbed audio. Offering both dubbed audio and translated captions maximizes accessibility for international audiences.
Review translations before synthesis
After Whisper transcription and Opus-MT translation, the translated text is displayed for review. You can edit any segment before triggering TTS synthesis. This is especially important for technical content, brand names, and idioms that machine translation may handle incorrectly.
Use for YouTube multi-language audio tracks
YouTube supports multiple audio tracks per video. Dub your content into 2-3 languages using Hearably Studio and upload each track as a separate audio option. Viewers see a language selector in the YouTube player — a powerful localization strategy with minimal effort.
Built for this exact use case
7 Languages at Launch
English, Spanish, German, French, Portuguese, Japanese, and Arabic. Each language pair uses a dedicated Opus-MT translation model and Piper TTS voice for high-quality output.
DSP Timbre Matching
Pitch extraction via autocorrelation + spectral envelope stamping via FFT. The dubbed voice retains the original speaker's tonal quality and pitch range — no 2GB neural voice cloning model required.
100% In-Browser Processing
No cloud upload, no server processing, no usage-based billing. The full pipeline (Whisper + Opus-MT + Piper TTS + DSP) runs in Web Workers inside your browser. Your video never leaves your device.
One-Time Model Download
Translation and TTS models are cached in the browser after first download. Subsequent dubbing sessions launch instantly with no network required. Process videos fully offline.
Choose your method
Different situations call for different tools. Hearably gives you both.
Chrome Extension
Enhance audio live while you stream. The extension intercepts your tab's audio and processes it in real-time — volume boost, EQ, presets — without downloading anything.
- Streaming on AI Voice Dubbing Online, Netflix, Spotify
- Video calls on Zoom, Meet, Teams
- Any website with audio
- When you want instant, always-on enhancement
Free Online Studio
Upload an audio or video file, apply volume boost + 10-band EQ, preview in real-time, then download the enhanced WAV. Your file never leaves your browser.
- Downloaded videos or music files
- Podcast episodes you want to boost before sharing
- Voice recordings, lectures, interviews
- When you need a permanently enhanced file
Pro tip: Use a YouTube-to-MP3 tool to download the audio, then enhance it in Hearably Studio with EQ + volume boost. Perfect for offline listening, DJ sets, or sharing on social media.
Three clicks to better audio
Install
Add Hearably from the Chrome Web Store. Under 300KB, installs in seconds.
Enhance
Click the Hearably icon and tap "Enhance." Boost kicks in instantly.
Enjoy
Adjust volume, EQ, and presets. Works on any website with audio.
Frequently asked questions
Does the video get uploaded to a server?
No. The entire dubbing pipeline — transcription, translation, speech synthesis, and timbre matching — runs locally in your browser. Your video file never leaves your device. You can verify this by disconnecting from the internet after the models are cached.
What languages are supported?
At launch: English, Spanish, German, French, Portuguese, Japanese, and Arabic. Additional language pairs will be added based on community demand. Each new language requires an Opus-MT translation model and a Piper TTS voice.
How does timbre matching work?
The system extracts the original speaker's pitch contour (via autocorrelation) and spectral envelope (via FFT). The TTS output is pitch-shifted to match the original pitch range, and the spectral envelope is stamped onto the TTS magnitudes. The result sounds like the original speaker reading the translated text — not a perfect clone, but significantly more natural than raw TTS.
How large are the model downloads?
The Whisper base model is approximately 74MB (downloaded once for all languages). Each translation model (Opus-MT) is 50-100MB per language pair. Each TTS voice (Piper) is approximately 60MB. Total for one language pair: ~190MB. Models are cached in the browser and reused across sessions.
Can I edit the translation before synthesis?
Yes. After Whisper transcription and Opus-MT translation, the translated text is displayed segment by segment. You can edit any segment before triggering TTS synthesis. This is essential for correcting machine translation errors in technical content or idiomatic expressions.
How does this compare to cloud dubbing services?
Cloud services (Papercup, Deepdub, Eleven Labs) offer higher-fidelity voice cloning using large neural models. However, they require cloud uploads, charge $50-150+/month with per-minute pricing, and process your content on external servers. Hearably runs entirely in-browser at EUR 9.99/month with no usage limits and complete privacy.
Does the dubbed audio maintain timing with the video?
The pipeline uses Whisper's timestamp data to align dubbed segments with the original speech timing. For most content, the alignment is close. However, translated text in some languages is longer or shorter than the original, which may require minor timing adjustments for perfect lip sync.
Can I dub a video into multiple languages?
Yes. Run the pipeline once for each target language. The Whisper transcription (Stage 1) is reused — only the translation, TTS, and timbre matching stages run for each additional language. Processing time scales linearly with the number of target languages.