Field Story

The Festival That Went Silent at 120Hz

At a 5,000-seat outdoor festival, the front-of-house engineer noticed a massive null around 120Hz during soundcheck. The subwoofer arrays were perfectly configured, but the measurement showed 18dB of cancellation. A quick transfer function measurement with SonaVyx revealed the problem: the two subwoofer stacks were 180° out of phase due to a polarity-reversed cable. One cable flip later, the low end came roaring back with flat response down to 40Hz. Total diagnosis time: 90 seconds.

Festival / Outdoor

Transfer Function Measurement per AES-2id: System Alignment

TL;DR

AES-2id provides recommendations for measuring room impulse responses and evaluating sound system performance. SonaVyx's dual-channel FFT analyzer computes H(f) = Gxy/Gxx with magnitude-squared coherence, phase, and group delay — all in real time via Rust WASM. This guide covers transfer function measurement for sound system alignment.

What is a Transfer Function?

A transfer function H(f) describes the frequency-dependent relationship between input and output of a system. In sound system measurement, it reveals:

  • Magnitude: How much the system boosts or cuts each frequency (frequency response)
  • Phase: The time delay per frequency (critical for multi-speaker alignment)
  • Coherence: How reliable the measurement is at each frequency

Measurement Setup

For a valid transfer function measurement:

  1. Feed the reference signal (pink noise or sweep) through the system
  2. SonaVyx captures both the reference (loopback or line) and the microphone signal
  3. The H1 estimator Gxy/Gxx computes the transfer function, minimizing output noise influence
  4. Coherence γ²(f) validates measurement quality per frequency

Reading the Results

The magnitude plot shows the system's frequency response in dB. A well-tuned system should show:

  • Smooth response within ±3 dB of target curve across the passband
  • Coherence above 0.8 across the measurement bandwidth
  • Smooth phase response (no abrupt jumps indicating time alignment issues)

Standard Reference

AES-2id:

Try It Now

Open this measurement tool in your browser — free, no download required.

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Last updated: March 19, 2026