Acoustic Doppler effect API

Computes the observed frequency for sound f' = f·(c±v_obs)/(c∓v_src) with a clear toward-positive sign convention, returning the frequency shift and pitch direction, and guarding the sonic-boom regime. Answers 'What pitch does a moving observer hear?', 'How much does an approaching siren shift?'.

Price$0.04per request

MethodPOST

Route/v1/engineering/doppler-sound

StatusLive

MIME typeapplication/json

Rate limit120/minute

Cache0s public

wavesacousticsdopplerfrequency-shiftsoundpitchsirenphysics

API URLhttps://x402.hexl.dev/v1/engineering/doppler-sound

Integration docs

Example request

{
  "sourceFrequencyHz": 440,
  "soundSpeedMps": 343,
  "sourceSpeedMps": 30
}

Example response

{
  "observedFrequencyHz": 482.172524,
  "sourceFrequencyHz": 440,
  "frequencyShiftHz": 42.172524,
  "soundSpeedMps": 343,
  "pitchChange": "higher (approaching)",
  "interpretation": "Observer hears 482.17 Hz (+42.17 Hz)."
}

Input schema

{
  "type": "object",
  "required": [
    "sourceFrequencyHz"
  ],
  "properties": {
    "sourceFrequencyHz": {
      "type": "number",
      "description": "Emitted frequency (Hz)",
      "examples": [
        440
      ]
    },
    "soundSpeedMps": {
      "type": "number",
      "description": "Speed of sound (default 343 m/s)",
      "examples": [
        343
      ]
    },
    "observerSpeedMps": {
      "type": "number",
      "description": "Observer speed toward source (m/s, default 0)",
      "examples": [
        0
      ]
    },
    "sourceSpeedMps": {
      "type": "number",
      "description": "Source speed toward observer (m/s, default 0)",
      "examples": [
        30
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}