Sample Rate

{
  "asOf": "2026-10-11T14:38:35.405Z",
  "commonUse": "CD audio",
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "guardBandAbove20kHz": 2050,
  "notChecked": [
    "the anti-aliasing and reconstruction filters of a real converter (which roll off before Nyquist)",
    "oversampling and sigma-delta converters, whose internal rate differs",
    "…2 more"
  ],
  "nyquistHz": 22050,
  "reasons": [
    "Aliased tones are indistinguishable from the lower frequency once sampled: filter before sampling.",
    "Alias frequency = |f - fs x round(f / fs)|."
  ],
  "samplePeriodMicroseconds": 22.6757,
  "sampleRate": 44100,
  "source": "Nyquist-Shannon sampling theorem, computed locally",
  "summary": "30000 Hz is above Nyquist (22050 Hz) and would alias to 14100 Hz.",
  "tone": {
    "aliasHz": 14100,
    "belowNyquist": false,
    "cyclesPerSample": 0.68027211,
    "frequencyHz": 30000,
    "periodMilliseconds": 0.03333333,
    "samplesPerCycle": 1.47
  },
  "verdict": "ALIASES"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://audio-calc.x402tookit.com/sample-rate?frequency=30000&sampleRate=44100'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://audio-calc.x402tookit.com/sample-rate?frequency=30000&sampleRate=44100' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Faudio-calc.x402tookit.com%2Fsample-rate
const res = await pay("https://audio-calc.x402tookit.com/sample-rate?frequency=30000&sampleRate=44100");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://audio-calc.x402tookit.com/sample-rate?frequency=30000&sampleRate=44100")
    print(res.status_code, res.text)