---
title: "Audio Frequency Analyzer"
slug: "audio-frequency-analyzer"
updated: 2026-02-26T07:59:48Z
published: 2026-02-26T07:59:48Z
---

> ## Documentation Index
> Fetch the complete documentation index at: https://composer.docs.vindral.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Audio Frequency Analyzer

The Audio Frequency Analyzer operator detects and verifies the presence of a specific audio frequency (such as a test tone) in an audio signal. It analyzes incoming audio to determine if a target frequency is present, measures consistency over time, and reports whether the signal matches expected parameters. This is useful for broadcast signal verification, quality control, and automated monitoring of audio feeds.

![Image](https://cdn.document360.io/94808959-fd66-406c-ab5e-4691ce952a14/Images/Documentation/image(243).png){height="" width=""}

---

## Overview

Audio frequency detection works by analyzing the incoming audio signal to:

- **Measure frequency** using zero-crossing detection to count wave cycles per second
- **Verify waveform shape** by calculating the crest factor (peak-to-RMS ratio) to confirm a clean sine wave
- **Track consistency** over a configurable time window to report signal stability

A pure sine wave has a crest factor of approximately 1.414 (√2). By checking this ratio, the operator can distinguish between a clean test tone and random noise or complex audio that happens to cross through the target frequency.

---

## Quick Start

1. Add the **Frequency Analyzer** operator to your audio processing chain
2. Set the **Frequency (Hz)** to match your expected test tone (e.g., 1000 Hz)
3. Adjust **Frequency Tolerance** to allow for minor drift (e.g., ±20 Hz)
4. Set **Minimum signal level** to ignore background noise
5. Monitor the **Match** indicator and **Consistency (%)** output

---

## Settings

### Configuration

| Setting | Description |
|---------|-------------|
| **Frequency (Hz)** | The target frequency to detect, in Hertz. Range: 50–5000 Hz. Common test tones include 400 Hz, 1000 Hz, and 1200 Hz. |
| **Frequency Tolerance** | Allowable deviation from the target frequency in Hz. For example, ±20 Hz means a 1000 Hz target will match frequencies between 980–1020 Hz. Range: 1–100 Hz. |
| **Shape Tolerance** | How strictly the waveform must match a pure sine wave. Lower values require a cleaner signal. A pure sine has a crest factor of 1.414; this setting defines how far from that value is acceptable. Range: 0.1–20.0. |
| **Minimum signal level (dB)** | The minimum amplitude threshold in decibels. Signals below this level are ignored to prevent false positives from background noise. Range: -36 to 0 dB. |
| **Window length (s)** | The time span in seconds used to calculate the consistency percentage and average frequency. Longer windows provide more stable readings but respond slower to changes. Range: 1–60 seconds. |

### Result

| Output | Description |
|--------|-------------|
| **Measured frequency** | The actual frequency detected in the audio signal, displayed in Hz. This is a weighted average over the analysis window. |
| **Match** | Boolean indicator showing whether the current audio matches the target frequency within tolerances and passes all validation checks. |
| **Consistency (%)** | Percentage of the analysis window duration where the signal matched the target. 100% means continuous match; lower values indicate intermittent signal. |

### Actions

| Action | Description |
|--------|-------------|
| **Reset** | Restores all configuration settings to their default values: 1000 Hz frequency, ±20 Hz tolerance, 0.1 shape tolerance, -12 dB minimum level, and 1 second window. |

---

## Workflow Guide

### Step 1: Identify Your Test Tone

Determine the frequency of the tone you need to detect:
- Standard broadcast test tone: 1000 Hz
- EBU alignment tone: 1000 Hz at -18 dBFS
- SMPTE alignment tone: 1000 Hz or 400 Hz
- Custom facility tones: Check your technical specifications

### Step 2: Configure Basic Settings

1. Set **Frequency (Hz)** to your target
2. Start with **Frequency Tolerance** at 20 Hz
3. Set **Minimum signal level** based on your expected tone level (typically -18 to -12 dB for alignment tones)

### Step 3: Adjust Shape Tolerance

1. If **Match** shows false when you know a tone is present:
   - Increase **Shape Tolerance** (try 1.0, then higher)
   - The tone may have harmonic distortion
2. If **Match** shows true on non-tone audio:
   - Decrease **Shape Tolerance** (try 0.1 or lower)
   - The detection is too lenient

### Step 4: Set Analysis Window

1. For real-time monitoring: Use 1–5 seconds
2. For stable long-term verification: Use 10–30 seconds
3. For quick detection response: Use 1 second

### Step 5: Interpret Results

- **Match = True, Consistency = 100%**: Stable, continuous tone detected
- **Match = True, Consistency < 100%**: Tone present but intermittent
- **Match = False, Consistency > 0%**: Tone was recently present but not currently
- **Match = False, Consistency = 0%**: No matching tone detected in the window

---

## Common Scenarios

### Broadcast Signal Verification

Monitoring a live broadcast feed for presence of a test tone before program start:
- Set **Frequency** to your station's standard tone (typically 1000 Hz)
- Use **Minimum signal level** of -20 dB to catch standard alignment levels
- Set **Window length** to 5 seconds for stable readings
- **Shape Tolerance** of 1.0 allows for minor transmission artifacts

### Equipment Testing

Verifying that audio equipment is passing a test tone correctly:
- Use tight **Frequency Tolerance** (±10 Hz) to catch frequency drift
- Set **Shape Tolerance** low (0.5 or less) to detect distortion
- **Window length** of 1 second for quick response
- Compare **Measured frequency** against the source to check for pitch shift

### Automated Failover Detection

Triggering alerts or switching when a tone disappears:
- Set **Consistency (%)** threshold in your automation system
- Use **Window length** of 3–5 seconds to avoid false triggers from brief dropouts
- **Minimum signal level** should be set just below your expected tone level

### Quality Control for Recorded Media

Checking that test tones in recorded files meet specifications:
- Use **Shape Tolerance** of 0.5 or lower to verify clean recordings
- **Frequency Tolerance** of ±5 Hz for precise verification
- Review **Measured frequency** to catch subtle pitch errors

---

## Troubleshooting

| Problem | Solution |
|---------|----------|
| **Match always False despite tone present** | Increase **Shape Tolerance** — the tone may have distortion. Also verify **Minimum signal level** isn't too high. |
| **Match True on speech/music** | Decrease **Shape Tolerance** to require a cleaner sine wave. Values of 0.5 or lower reject complex audio. |
| **Measured frequency fluctuates** | Increase **Window length** for more averaging, or the source tone may be unstable. |
| **Consistency never reaches 100%** | Short dropouts or level variations may cause momentary failures. Increase **Shape Tolerance** or decrease **Minimum signal level** slightly. |
| **Wrong frequency detected** | Check that both stereo channels contain the tone. The operator averages both channels. |
| **No detection on very low frequencies** | Frequencies below 100 Hz need longer audio frames to detect accurately. This operator works best above 100 Hz. |
| **False positives on silence** | Increase **Minimum signal level** to reject low-level noise. Try -24 dB or higher. |

---

## Tips for Best Results

### Signal Quality

- Use the cleanest signal path possible for test tones
- Avoid heavy compression or limiting on tone signals

### Tolerance Settings

Start with moderate tolerances and tighten as needed:
- **Frequency Tolerance**: Begin at ±20 Hz, reduce if false positives occur
- **Shape Tolerance**: Begin at 1.0, reduce for stricter verification

### Stereo Considerations

The operator analyzes both left and right channels independently and requires both to match for a positive result. Ensure your test tone is present on both channels, or the signal is properly configured as dual-mono.

### Continuous Monitoring

For long-running verification:
- Use **Window length** of 10+ seconds for stable readings
- Monitor **Consistency (%)** rather than instantaneous **Match** for trend analysis
- Consider logging results for later review

---

## Technical Notes

- Audio is processed at 48 kHz sample rate
- Zero-crossing detection counts positive-going crossings only
- Crest factor for ideal sine wave: √2 ≈ 1.41421356
- Both stereo channels must pass all checks for Match to be True
- History is maintained using a sliding window queue weighted by frame duration
- The operator passes audio through unchanged — it monitors but does not modify the signal