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Performance of LISNR Tones (Signal Strength/Quality)
Performance of LISNR Tones (Signal Strength/Quality)

Is there a way to quantify how strong an incoming LISNR Tone transmission is?

Warren Williams avatar
Written by Warren Williams
Updated over a week ago

When the Radius SDK demodulates/receives an incoming tone, the following values are available from the Tone object:

  • Signal-to-Noise Ratio (SNR): Indicates in decibels (dB) the amount of interfering noise relative to the received strength of the LISNR Tone.

  • Header and Payload Error Vector Magnitude (EVM): Gives an indication in decibels (dB) of how challenging it was for the LISNR Tone to be received by the LISNR Radius SDK.

    • Header EVM: EVM value indicating the quality of the Header.

    • Payload EVM: EVM value indicating the quality of the Payload.

    • These values are only available when receiving PKAB2 or PKAB2_wideband tones. Standard2 and Standard2_wideband tones will not have a header/payload EVM value.

  • (Future) In the release of Radius 3.0, there will be additional callbacks to indicate when the start of a playing tone is detected (useful for if a long transmission is incoming) and a callback to indicate when a tone has failed to be demodulated (useful for providing UX/UI feedback to the user to hold their phone steady, move closer, etc.). Ask our Customer Success team ( about release dates.

Below is a relative scale to indicate how SNR and EVM (db) values can be associated used to measure how easy/challenging it was to receive a tone.


  • Default values for an unknown signalToNoiseRatio will give the default value of -60.0

Developers using the Radius SDK can use the SNR and EVM values to provide UI/UX indicators or messaging to their end users. If you are experiencing either poor SNR or EVM values, the following actions are recommended:

  • Transmit at a higher volume.

  • Reduce the distance between the transmitting speaker and the receiving microphone.

  • Angle the transmitting speaker and receiving microphone towards each other and ensure there is nothing obstructing the line of sight.

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