# Measurement & validation

Python tools to exercise and characterize the finished amplifiers through a PC sound card.

| Script | Purpose |
|--------|---------|
| [`generate_test_signals.py`](generate_test_signals.py) | Build 1 kHz sine, pink noise, and 20 Hz–20 kHz log sweep WAVs |
| [`measure_thd.py`](measure_thd.py) | FFT THD / THD+N from a 1 kHz recording (or live capture) |
| [`plot_frequency_response.py`](plot_frequency_response.py) | Sweep deconvolution → FR plot + CSV |

## Setup

```bash
cd measurement
python3 -m venv .venv
source .venv/bin/activate
pip install -r requirements.txt
# Optional for live I/O: system PortAudio (e.g. apt install libportaudio2)
```

## Safety

**Never** feed speaker-level voltages straight into a sound-card line input. Use a resistive attenuator / divider (see comments in `measure_thd.py`). Incorrect hookup can destroy the PC interface and is a shock hazard on high-power rails.

## Typical session

```bash
python generate_test_signals.py --outdir wav_out --duration 10
# Play wav_out/sine_1kHz.wav through crossover → amp → attenuator → record
python measure_thd.py --wav capture_1k.wav --f0 1000
# Play sine_sweep_20_20k.wav, record, then:
python plot_frequency_response.py \
  --recorded capture_sweep.wav \
  --reference wav_out/sine_sweep_20_20k.wav \
  --out fr_mid.png
```