FFT Bin Width / Frequency Resolution Calculator implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-clean

Evidence ID

t4-220

Effect

Computation or source lookup only

Input and validation requirements

A zero sample rate creates an undefined time resolution and must be rejected. The calculator is also vulnerable to a 1000-fold frequency and time error when a value such as 44.1 lacks an explicit Hz/kHz convention.

Required corrections

No binding erratum is attached to this unique-name record. Implementers must still preserve the declared units, domain, and failure behavior.

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "sample_rate_hz": 48000,
    "fft_size": 1024,
    "window": "rectangular"
  },
  "expected_outputs": {
    "bin_width_hz": 46.875,
    "time_resolution_s": 0.0213333333333333,
    "bin_center_frequency_checks_hz": {
      "k=0": 0,
      "k=1": 46.875,
      "k=512": 24000,
      "k=1023": 47953.125
    }
  },
  "working": "Δf = f_s/N = 48000/1024 = 46.875 Hz. time_resolution = N/f_s = 1024/48000 = 0.0213333333333333 s = 21.3333333333333 ms. bin_0 = 0×46.875 = 0 Hz. bin_1 = 1×46.875 = 46.875 Hz. bin_512 = 512×46.875 = 24000 Hz. bin_1023 = 1023×46.875 = (1024−1)×46.875 = 48000−46.875 = 47953.125 Hz. The raw first-N sequence is k×46.875 for k=0..1023."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche4/tranche4-results.json