---
source_path: "reference/voicehub.md"
canonical_url: "https://doc.sensory.com/tnl/7.8/reference/voicehub/"
---

# VoiceHub

[Sensory's VoiceHub][vh] is a web portal that provides a convenient interface for
developers to prototype and experiment with wake words, language models and natural
language understanding. Users can build custom wake words, voice control command sets, and
create grammar-based language models with flexible intents and entities.

VoiceHub uses Sensory's [TrulyHandsfree][thf] for wake words and spotted commands,
and [TrulyNatural][tnl-lite] for grammar-based recognition with natural language
markup to identify intents and entities.

## Output format selection

VoiceHub can deliver recognizer models in various formats, as specified by the `Output Format`
selector. If you want to use such a model with the TrulyHandsfree or TrulyNatural SDKs
you should select the `THF/TNL SDK: snsr file` option. This is the default for new projects.

If you are using TrulyHandsfree or TrulyNatural on a small embedded platform,
you should select one of the alternate output formats described below.

**`THF/TNL SDK: snsr file`** _(recommended)_

- This is the standard TrulyNatural model format. Use this unless you will be running the model
  on an embedded platform with limited CPU cycles and available RAM.

**`THF/TNL SDK: snsr file (low memory use)`**

- This optimizes the model for small platforms with limited CPU cycles (< 500 MHz)
  and RAM (< 1 MiB of heap). The reduced heap and CPU requirements come at the expense
  of a bit of recognition accuracy.

**`THF/TNL SDK: .c file (low memory use)`**

- Similar to `THF/TNL SDK: snsr file (low memory use)` above, but also includes a model converted
  to C code that you can compile into your application. On platforms with read-only / flash
  memory this reduces the amount of RAM required by the size of the model file.
- VoiceHub uses [snsr-edit](https://doc.sensory.com/tnl/7.8/tools/snsr-edit.md#snsr-edit) to create two C files from the `snsr` model:
    - `snsr-edit -c voicehub -t model.snsr` to create _model.c_, and
    - `snsr-edit -i -t model.snsr -o model-custom-init.c` to create _model-custom-init.c_. This file
      includes custom initialization code that elides unused modules at link time to [reduce overall
      application size](https://doc.sensory.com/tnl/7.8/faq.md#reduce-code-size).

**`THF/TNL SDK: .c file (low memory use for ST Micro STM32H7)`**

- Similar to `THF/TNL SDK: .c file (low memory use)`, but also includes TrulyNatural SDK libraries
  for use on the STMicroelectronics [STM32H7][] series microcontrollers.

**`Embedded: Arm Cortex-M55/M85 Ethos-U55-128`**

- Similar to `THF/TNL SDK: .c file (low memory use)`, but with inference optimized for Arm's
  Cortex-M55/M85 and [Ethos-U55][] NPU with [Vela][] accelerator config `ethos-u55-128`.
- Use this on the [Alif Ensemble][] family of microcontrollers.

**`Embedded: Arm Cortex-M55/M85 Ethos-U55-256`**

- Similar to `THF/TNL SDK: .c file (low memory use)`, but with inference optimized for Arm's
  Cortex-M55/M85 and [Ethos-U55][] NPU with [Vela][] accelerator config `ethos-u55-256`.
- Use this on the [Alif Ensemble][] family of microcontrollers.

**`Embedded: Infineon Arm Cortex-M55/M85 Ethos-U55-128 (model in RAM)`**

- Similar to `THF/TNL SDK: .c file (low memory use)`, but with inference optimized for Arm's
  Cortex-M55/M85 and [Ethos-U55][] NPU with [Vela][] accelerator config `ethos-u55-128`.
- The compiled model code runs from RAM. This requires more available heap than the
  `(model in ROM/Flash)` option below. Use this only if the flash read speed is too low
  to allow the model to run in real time.
- Use this only on Infineon microcontrollers.

**`Embedded: Infineon Arm Cortex-M55/M85 Ethos-U55-128 (model in ROM/Flash)`**

- Similar to `THF/TNL SDK: .c file (low memory use)`, but with inference optimized for Arm's
  Cortex-M55/M85 and [Ethos-U55][] NPU with [Vela][] accelerator config `ethos-u55-128`.
- The compiled model code runs from code space.
- Use this only on Infineon microcontrollers.

<!-- Reference definitions from includes/links.md -->
[Alif Ensemble]: https://alifsemi.com/products/ensemble/ "The Alif Ensemble family of Arm-based 32-bit microcontrollers"
[Ethos-U55]: https://developer.arm.com/Processors/Ethos-U55 "Arm Ethos-U NPU family"
[STM32H7]: https://www.st.com/en/microcontrollers-microprocessors/stm32h7-series.html
[thf]: https://www.sensory.com/wake-word/ "Low Power Wake Words & Phrase Recognition Engine"
[tnl-lite]: https://www.sensory.com/natural-language-understanding/ "Large Vocabulary Continuous Speech Recognition (LVCSR) with Dynamic Natural Language Understanding"
[Vela]: https://developer.arm.com/documentation/109267/0102/Tool-support-for-the-Arm-Ethos-U-NPU/Ethos-U-Vela-compiler "Ethos-U Vela compiler"
[vh]: https://www.sensory.com/voicehub/ "Create a custom voice recognizer quickly and easily"

<!-- Abbreviation definitions from includes/abbreviations.md -->
*[RAM]: Random Access Memory
*[ROM]: Read-Only Memory, typically nonvolatile flash memory
*[SDK]: Software Development Kit
*[THF]: TrulyHandsfree, Sensory's wake word and command recognition technology
*[TNL]: TrulyNatural, Sensory's large-vocabulary speech recognition technology