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It cannot be overstated how important microphone type, placement, and calibration are for accurate and reliable speech recognition. This page outlines best practices to help make sure you get this right.
Please ensure your audio files conform to the specifications listed here.Let us know if you need help with audio recording best practices!

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Environment

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Microphone Type

  • Use directional microphones for dictation.
  • Use beamforming array microphones for ambient conversations.
Goal is to focuses on the primary speaker(s) and suppresses background noise.

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Microphone Placement

  • Keep the microphone near the side of your mouth so you do not breathe directly into it.
  • A distance of 10–20 cm for dictation is ideal, or within 1 m for doctor/patient conversation.
Goal is to balances clarity and comfort.

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Microphone Calibration

  • Ensure proper gain adjustment is used per workflow needs (e.g., near-field for dictation and far-field for ambient conversations)
  • Recalibrate when changing environments or if audio quality issues are detected.
  • Consider use of auto gain adjustment in ambient workflows.
Gain adjustment based on audio capture environment, workflow, and speaker diction pattern is essential for capturing audio at the correct volume.

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Ambient Noise and Reverberation

  • Keep background noise below 40 dBA (quiet office).
  • Use rooms with carpeted, non-reflective surfaces when possible.
Goal is to prevent unintentional audio, or echos/ reverberations, from being picked up by speech to text as they can harm accuracy or diarization.

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Use of Built-in Laptop Mics

  • Avoid when possible: They can capture keyboard and fan noise.
Use microphones that connect via USB cables for best reliability. These can be desktop, wearable/ headset, or handheld devices.

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Use of Bluetooth Mics

  • Use with caution: Ensure battery life and wireless range are sufficient for your needs.
Note that being out of range or low battery may cause issues with transmission of audio packets!

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Use of Mobile Devices

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iPhones and iPads

Modern iOS devices have high-quality MEMS microphone arrays and can deliver professional speech to text results if configured correctly:
  • Use Voice Memos app or any third-party app (like Corti Assistant) that exports uncompressed WAV, FLAC, or Opus
  • 16-bit / 16 kHz PCM Mono audio format
  • Use the microphone on the bottom of the device as the primary microphone (talk towards where you would speak for a phone call, not the screen or top/side array mic)
  • Disable Voice Isolation or Wide Spectrum as these apply aggressive filters that can distort audio quality
  • Leave system gain fixed (do not rely on iOS loudness compensation) in order to prevent dynamic gain shifts that disrupt speech to text input consistency
  • If possible, explore wired or MFi-certified microphones for optimal audio quality capture
Be mindful of cases that may obstruct the microphone!

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Android Devices

  • Android devices have variable microphone hardware, but most of the guidelines for iPhones listed above can be applied.

Please contact us if you need help with supported audio formats or audio quality concerns.