audio-fft-sanity

audio-fft-sanity is a skill for Claude Code from gertsylvest/meta-team. It costs 52 tokens per session (664 once invoked), scanned A, original, MIT.

An audio-file analysis check that uses frequency analysis, commonly called an FFT, to inspect the quality and correctness of generated audio.

In plain words
What is it for?
Use it after offline C tests or browser audio captures to check fundamental frequency, total harmonic distortion, signal-to-noise ratio, clipping, and silence.
Why use it?
It catches silent output, clipping, incorrect frequencies, distortion, and excess noise that ordinary code tests may miss.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: positional $N argument.

Good fit Use it after offline C tests or browser audio captures to check fundamental frequency, total harmonic distortion, signal-to-noise ratio, clipping, and silence.

Compare 6 skills from other repositories ↓
Install with agentmods
npx agentmods add skills/gertsylvest/meta-team/audio-fft-sanity
Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

Any agent
npx skills add gertsylvest/meta-team --skill audio-fft-sanity
Clone the repo
git clone --depth 1 https://github.com/gertsylvest/meta-team

Made for: Claude Code.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for audio-fft-sanity

README.md
[![agentmods](https://agentmods.dev/badge/skills/gertsylvest/meta-team/audio-fft-sanity/github.svg)](https://agentmods.dev/skills/gertsylvest/meta-team/audio-fft-sanity)
Your own site
<a href="https://agentmods.dev/skills/gertsylvest/meta-team/audio-fft-sanity"><img src="https://agentmods.dev/badge/skills/gertsylvest/meta-team/audio-fft-sanity/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for audio-fft-sanity

Your own site · 80×15
<a href="https://agentmods.dev/skills/gertsylvest/meta-team/audio-fft-sanity"><img src="https://agentmods.dev/badge/skills/gertsylvest/meta-team/audio-fft-sanity.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 52 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 664 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00052 $0.00664
Opus 5 $0.00026 $0.00332
Sonnet 5 $0.00010 $0.00133
Haiku 4.5 $0.00005 $0.00066

Measured 11d ago against content hash a09dee26fd14, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-11, from the pricing page.

Security

Grade A, and why

audio-fft-sanity scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 11d ago.

The scan reads SKILL.md. This mod also ships 1 executable file (analyse.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

library/skills/audio-fft-sanity/SKILL.md · 69 lines

How it starts

The opening of the file, as written. The whole thing — 69 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Audio FFT Sanity Check

Run a suite of FFT-based assertions on an audio output file to confirm a signal chain is behaving correctly. Suitable for both offline C test output and WASM OfflineAudioContext captures.

Requirements

  • Python 3.8+
  • numpy and scipy: pip install numpy scipy

Instructions

Arguments are in $ARGUMENTS. Pass them directly to the analysis script:

python3 "$(dirname "$0")/analyse.py" $ARGUMENTS

Checks performed

Check What it detects
CLIPPING Any sample magnitude > 0.99 — indicates gain staging problem or overflow
SILENCE RMS below -60 dBFS — catches zero-output bugs (uninitialised buffer, wrong pointer)
FUNDAMENTAL Detected peak frequency vs --freq (if given) — verifies oscillator/filter tuning
THD Total harmonic distortion (harmonics 2–5 vs fundamental) — catches nonlinear distortion or aliasing
SNR Signal-to-noise ratio estimate — catches noise floor issues or quantisation problems

Exit codes

  • 0 — all checks passed
  • 1 — one or more checks failed

Examples

# Basic smoke test — check for clipping, silence, SNR, THD with defaults
python3 analyse.py output.wav

# Verify a 440 Hz sine from a synth, strict THD limit
python3 analyse.py output.wav --freq 440 --thd-max 1.0 --snr-min 60

# Raw float32 file at 48 kHz, stereo interleaved (uses first channel)
python3 analyse.py output.f32 --sr 48000 --channels 2 --freq 1000

Typical usage patterns

Synthesizer test: Run the synth at a known pitch (e.g. MIDI A4 = 440 Hz), render N frames to a float32 file, then:

python3 analyse.py synth_output.wav --freq 440 --thd-max 2.0 --snr-min 50

Effect processor test (e.g. filter, EQ): Feed a broadband noise or sweep, capture output — omit --freq and check only for clipping and SNR:

python3 analyse.py filtered_output.wav --snr-min 30

Impulse response capture: Feed a single-sample impulse, check output is non-silent and not clipping:

python3 analyse.py ir_output.wav

Read the full file on GitHub · 69 lines

Files

What ships with it

1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 11d ago First seen · 69 lines · 52 tokens per session scan A a09dee26fd14

Subscribe to this mod's changes

audio-fft-sanity is a skill published in the GitHub repository gertsylvest/meta-team (5 stars, last pushed 1mo ago), licensed MIT. It adds 52 tokens to every session and 664 once invoked, about $0.0003 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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