{
  "slug": "speaker-spl-distance",
  "title": "Speaker SPL Distance Calculator",
  "heading": "Speaker SPL Drop-Off Distance Calculator",
  "category": "other",
  "url": "https://www.revenuelab.fyi/toolbox/speaker-spl-distance",
  "summary": "Estimate sound pressure level at any distance from a speaker.",
  "description": "Sound pressure level (SPL) drops with distance according to the inverse square law in free field — roughly 6 dB for every doubling of distance outdoors, though indoor reverberant spaces lose less due to reflections. This calculator takes a speaker's rated SPL at a reference distance (usually 1 meter, printed on the spec sheet) and projects the level at your actual mix position or back-of-room distance, which is the real number that determines whether your PA is loud enough where it counts.",
  "formula": "SPL at distance = SPL at reference − 20 × log10(distance ÷ reference distance).",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=speaker-spl-distance",
  "inputs": [
    {
      "id": "refSpl",
      "label": "Rated SPL at reference distance",
      "kind": "number",
      "hint": null,
      "default": 132,
      "unit": "dB",
      "min": 60,
      "max": 160
    },
    {
      "id": "refDistance",
      "label": "Reference distance",
      "kind": "number",
      "hint": null,
      "default": 1,
      "unit": "m",
      "min": 0.1,
      "max": null
    },
    {
      "id": "targetDistance",
      "label": "Distance to listener",
      "kind": "number",
      "hint": null,
      "default": 20,
      "unit": "m",
      "min": 0.1,
      "max": null
    }
  ],
  "outputs": [
    {
      "id": "spl",
      "label": "Estimated SPL at listener",
      "format": "decimal",
      "hint": null,
      "primary": true
    },
    {
      "id": "dbLoss",
      "label": "Total dB lost over distance",
      "format": "decimal",
      "hint": null,
      "primary": false
    },
    {
      "id": "doublingLoss",
      "label": "dB lost per distance doubling (free field)",
      "format": "number",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Rated SPL at reference distance: 132 dB",
      "Reference distance: 1 m",
      "Distance to listener: 20 m"
    ],
    "outputs": [
      "Estimated SPL at listener: 106",
      "Total dB lost over distance: 26",
      "dB lost per distance doubling (free field): 6"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter rated spl at reference distance (dB).",
      "Enter reference distance (m).",
      "Enter distance to listener (m).",
      "Read your estimated spl at listener on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "refSpl": 79,
        "refDistance": 0.6,
        "targetDistance": 12
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "refSpl": 132,
        "refDistance": 1,
        "targetDistance": 20
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "refSpl": 160,
        "refDistance": 1.6,
        "targetDistance": 32
      }
    }
  ],
  "limitations": [
    "Estimates assume standard, average conditions — local rules, pricing, and materials vary.",
    "Results are rounded for readability; add a buffer before ordering, booking, or committing.",
    "Double-check anything with a real cost attached against a local quote."
  ],
  "faq": [
    {
      "q": "Why 6 dB per doubling of distance and not something else?",
      "a": "The inverse square law states sound intensity falls off with the square of distance in a free field, which works out to a 6 dB drop in SPL every time you double the distance from the source. Indoors, reflected sound partially compensates, so real-world loss is often closer to 3-4 dB per doubling in reverberant rooms."
    },
    {
      "q": "What SPL level is safe for an audience over a full show?",
      "a": "OSHA and hearing-health guidelines generally recommend average levels under 100-105 dB for extended exposure without hearing protection, with peak levels ideally not exceeding 115 dB even briefly. Mix engineers commonly target 95-102 dB average at front-of-house for live rock shows."
    },
    {
      "q": "Does this formula account for outdoor wind and humidity?",
      "a": "No — this is the idealized free-field inverse square model. Wind, humidity, temperature gradients, and ground absorption all add extra attenuation outdoors, especially at high frequencies over long distances, so treat the result as a best-case estimate for outdoor shows."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/pa-power-sizing",
    "https://www.revenuelab.fyi/toolbox/db-attenuation"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Speaker SPL Distance Calculator (https://www.revenuelab.fyi/toolbox/speaker-spl-distance)"
}