# Audio Calc SPL Distance

> Audio Calc SPL Distance is a paid API for AI agents from audio-calc.x402tookit.com, paid per call via x402, $0.02/call, status unknown (last checked 2026-10-30).

Calculates sound pressure level at a new distance or finds the distance for a target dB level using the inverse-square law (6 dB per doubling for point sources, 3 dB per doubling for line sources).

## Facts

- Endpoint: GET https://audio-calc.x402tookit.com/spl-distance?utm_source=zero.xyz
- Price: $0.02/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-30
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/audio-calc-spl-distance-af7c590f
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xdDJ62dVt3cCkOVoQ0q1V

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability audio-calc-spl-distance-af7c590f
```

Example prompt: If a speaker measures 94 dB at 1 metre, what will the SPL be at 25 metres away, assuming it's a point source?

## When to prefer this

Use this endpoint when you need to apply the inverse-square law (or cylindrical spreading for line sources) to predict how sound level changes with distance, or to find the distance at which a source reaches a target dB level. It is the right choice for acoustic planning, noise impact assessments, PA system design, or safety distance calculations. Prefer this over manual calculation when you need physical output quantities like pressure in Pascals or intensity in W/m² alongside the dB result.

## Known failure modes

- Missing required 'level' query parameter returns an error
- Neither 'distance' nor 'targetDb' provided — endpoint needs at least one of these to compute a result
- Negative or zero distance values may produce invalid or undefined results
- Extremely large distances may yield physically implausible results below noise floor without warning

## How this service works

Sound level at another distance (inverse-square law; line sources fall 3 dB per doubling), or the distance for a level.

## Output

Returns the computed SPL in dB at the requested distance (or the distance for a target dB), along with the change in dB from the reference level, pressure in Pascals, intensity in W/m², dB per doubling, spreading type (point or line), sound power level for point sources, reference distance, and a plain-language summary.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "level"
     ],
     "properties": {
      "level": {
       "type": "number",
       "description": "Sound pressure level in dB measured at refDistance"
      },
      "source": {
       "enum": [
        "point",
        "line"
       ],
       "type": "string",
       "description": "point (default, 6 dB per doubling) or line (3 dB per doubling)"
      },
      "distance": {
       "type": "number",
       "description": "Distance in metres to find the level at (use this, or targetDb)"
      },
      "targetDb": {
       "type": "number",
       "description": "A level in dB to find the distance for"
      },
      "refDistance": {
       "type": "number",
       "description": "Distance of the measurement in metres (default 1)"
      }
     }
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "asOf": {
       "type": [
        "null",
        "string"
       ]
      },
      "source": {
       "type": [
        "null",
        "string"
       ]
      },
      "levelDb": {
       "type": [
        "null",
        "number"
       ]
      },
      "reasons": {
       "type": [
        "array",
        "null"
       ],
       "items": {
        "type": "string"
       }
      },
      "summary": {
       "type": [
        "null",
        "string"
       ]
      },
      "verdict": {
       "type": [
        "null",
        "string"
       ]
      },
      "changeDb": {
       "type": [
        "null",
        "number"
       ]
      },
      "degraded": {
       "type": [
        "boolean",
        "null"
       ]
      },
      "distanceM": {
       "type": [
        "null",
        "number"
       ]
      },
      "spreading": {
       "type": [
        "null",
        "string"
       ]
      },
      "disclaimer": {
       "type": [
        "null",
        "string"
       ]
      },
      "notChecked": {
       "type": [
     
… (truncated)
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/audio-calc-spl-distance-af7c590f/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from audio-calc.x402tookit.com](https://www.zero.xyz/host/audio-calc.x402tookit.com/llms.txt)