← The evidence ledger
Evidence row 2202257
Observed , by sync.x402_bazaar/1.
- Kind
- listing
- About
- source_record x402_bazaar:https://audio-calc.x402tookit.com/sample-rate
- Recorded
- Previous row
- None: the first of its kind about this subject
- Body SHA-256
- dce8fe209a78cf66d95b846af3219870447af4cf3951fba9ad42fa9733fc4b0c
- Leaf
- 0x1cdcafcf3668da4b0fba448875a2256d090960afb4b5caa4ef802e9c8b84bcaf
What was observed
{
"endpoints": [
[
"x402",
"https://audio-calc.x402tookit.com/sample-rate"
]
],
"name": "Audio Calc",
"owner_address": "0xb531320805c5bed1d46aeadcf4f008fdf172dbda",
"raw": {
"accepts": [
{
"amount": "20000",
"asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
"extra": {
"name": "USD Coin",
"version": "2"
},
"maxTimeoutSeconds": 300,
"network": "eip155:8453",
"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"scheme": "exact"
},
{
"amount": "20000",
"asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
"extra": {
"feePayer": "D6ZhtNQ5nT9ZnTHUbqXZsTx5MH2rPFiBBggX4hY1WePM",
"transactionVersions": [
0
]
},
"maxTimeoutSeconds": 300,
"network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
"payTo": "DUPiupXtuox38dcGoXUKer5mAydCzmaHjrbQ66qeEm8s",
"scheme": "exact"
},
{
"amount": "20000",
"asset": "0x3c499c542cEF5E3811e1192ce70d8cC03d5c3359",
"extra": {
"name": "USD Coin",
"version": "2"
},
"maxTimeoutSeconds": 300,
"network": "eip155:137",
"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"scheme": "exact"
},
{
"amount": "20000",
"asset": "0xaf88d065e77c8cC2239327C5EDb3A432268e5831",
"extra": {
"name": "USD Coin",
"version": "2"
},
"maxTimeoutSeconds": 300,
"network": "eip155:42161",
"payTo": "0xb531320805C5BED1D46AEaDcF4F008FDF172DBDa",
"scheme": "exact"
}
],
"description": "Nyquist frequency for a sample rate, plus the alias frequency and samples per cycle of a tone, and the guard band above 20 kHz.",
"extensions": {
"bazaar": {
"info": {
"input": {
"method": "GET",
"queryParams": {
"frequency": 30000,
"sampleRate": 44100
},
"type": "http"
},
"output": {
"example": {
"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"
},
"type": "json"
}
},
"schema": {
"$schema": "https://json-schema.org/draft/2020-12/schema",
"properties": {
"input": {
"additionalProperties": false,
"properties": {
"method": {
"enum": [
"GET"
],
"type": "string"
},
"queryParams": {
"properties": {
"frequency": {
"description": "Optional tone frequency in Hz to check for aliasing",
"type": "number"
},
"sampleRate": {
"description": "Sample rate in Hz, for example 44100",
"type": "number"
}
},
"required": [
"sampleRate"
],
"type": "object"
},
"type": {
"const": "http",
"type": "string"
}
},
"required": [
"type",
"method"
],
"type": "object"
},
"output": {
"properties": {
"example": {
"properties": {
"asOf": {
"type": [
"null",
"string"
]
},
"commonUse": {
"type": [
"null",
"string"
]
},
"degraded": {
"type": [
"boolean",
"null"
]
},
"disclaimer": {
"type": [
"null",
"string"
]
},
"guardBandAbove20kHz": {
"type": [
"null",
"number"
]
},
"notChecked": {
"items": {
"type": "string"
},
"type": [
"array",
"null"
]
},
"nyquistHz": {
"type": [
"null",
"number"
]
},
"reasons": {
"items": {
"type": "string"
},
"type": [
"array",
"null"
]
},
"samplePeriodMicroseconds": {
"type": [
"null",
"number"
]
},
"sampleRate": {
"type": [
"null",
"number"
]
},
"source": {
"type": [
"null",
"string"
]
},
"summary": {
"type": [
"null",
"string"
]
},
"tone": {
"properties": {
"aliasHz": {
"type": [
"null",
"number"
]
},
"belowNyquist": {
"type": [
"boolean",
"null"
]
},
"cyclesPerSample": {
"type": [
"null",
"number"
]
},
"frequencyHz": {
"type": [
"null",
"number"
]
},
"periodMilliseconds": {
"type": [
"null",
"number"
]
},
"samplesPerCycle": {
"type": [
"null",
"number"
]
}
},
"type": [
"null",
"object"
]
},
"verdict": {
"type": [
"null",
"string"
]
}
},
"type": "object"
},
"type": {
"type": "string"
}
},
"required": [
"type"
],
"type": "object"
}
},
"required": [
"input"
],
"type": "object"
}
}
},
"lastUpdated": "2026-11-01T22:36:49.026Z",
"quality": {
"l30DaysTotalCalls": 2,
"l30DaysUniquePayers": 2,
"lastCalledAt": "2026-11-01T22:36:48.863Z"
},
"resource": "https://audio-calc.x402tookit.com/sample-rate",
"serviceName": "Audio Calc",
"tags": [
"audio",
"sample-rate",
"nyquist",
"aliasing"
],
"type": "http",
"x402Version": 2
},
"source": "x402_bazaar",
"summary": "Nyquist frequency for a sample rate, plus the alias frequency and samples per cycle of a tone, and the guard band above 20 kHz."
}What the leaf hashes
{"body":"dce8fe209a78cf66d95b846af3219870447af4cf3951fba9ad42fa9733fc4b0c","id":2202257,"kind":"listing","method":"sync.x402_bazaar/1","observed_us":1793646814761170,"prev":null,"subject":"x402_bazaar:https://audio-calc.x402tookit.com/sample-rate","subject_kind":"source_record"}Proof
Fold these into the leaf in order, hashing each sorted pair with keccak256, to reach the root of (444186 rows).
- 0x1cdcbdec046b7363bb5a00fc0d5a561a0bf82edd10b5542547679e65fd50dd82
- 0x5cec2ad8ae6a7e25625930d1aed62dd639553aae7d46314c08d8780c49074a96
- 0x0c658a35cb8f6bfa9c7f1183cf39176b079e99ee3fb35c921e7980d37b05681f
- 0x046fb82ae88a71c8a42e7359a7cb76f7ad7b7822654c25e41c1619956eaf3c12
- 0x17f04357a0e58442c9e6c50e9965c3e170f8f5192f72e3d0137d2963e4f96801
- 0x4cb0157439cfd936284ebbd207a5572abe23784d5a9c5b8a4dc01d35dc5cdd05
- 0xcefb8a4f9f6f1078cb06cebf7e00b634f6b99d3d69d004e95db677846d7301bc
- 0xebd510f5ae18e5541bf7454f0231a59dae76dce3ffda8ed7a827c85c3b02c17b
- 0xc51fd4847ddb71c2396e633557a909318674cda31f814a89da38bd88d6c958fc
- 0x35b7be1aebd65b161a90b5f8ee0c4bc3f5b2f9909d530453d65328ebc4ae4e03
- 0x1958dba7b75c9cafc665741f77e7dcaa26c468963f73c107738b97fbcb474191
- 0xfa646e4b5dbdebf795dfda0b29a3ea57332f8666459a0c2538f16fe8103169aa
- 0xd6cbf3765149b25eba4e10fe21fd5993687ecdd3cb9c495f97c3c148afee08ed
- 0xc63937235d47ff2107de3051477e395be67b96d91d1349c787bf4b1ef91b602f
- 0xcd21ec8d72a18a2d4513e4fd309abbb530810fb1dbeecd4b9b85acb4d6ff8f12
- 0xac40f077ca4be8c3432a67771725cc315e8101fc2649999cfad2c900a7640e27
- 0x53a741b69e9e51c4a288a74712aa6ac3fb28c8923cd3e6461d161c4f2d48b31a
- 0x050f2978b537f7afb21ee1551577cdf146d1c56f4df12d24315ae5e69366b0a4
- 0x365b161a4b68d750dcc4b3ecce1154a2163c87b08762079428e68f0ebb6a754e
- Day root
- 0x78fecaabbe319e56f5c4b80fc02e2052e198ad24781da8832a475ff65f2002d1
- Chained
- 0xdc35957db5d1371ca382b9152878ffece28ec7c5cb4f98fd71ddb367f8b999b2
- Published
- On Arc Testnet, block 70432815: 0x56b814612eb2e3e544153df3e91e1f7199106d1e430c7d8c6b653feeb9ebe9af