# Phase 2: Audio Synthesis Engine - Discussion Log

> **Audit trail only.** Do not use as input to planning, research, or execution agents.
> Decisions are captured in CONTEXT.md — this log preserves the alternatives considered.

**Date:** 2026-03-26
**Phase:** 02-audio-synthesis-engine
**Areas discussed:** Tone mapping, Waveform texture, Amplitude dynamics, Mixing & headroom

---

## Tone Mapping

### Frequency range

| Option | Description | Selected |
|--------|-------------|----------|
| Narrow ambient (80-400 Hz) | Deep, bass-heavy drones — everything in warm low register | |
| Wide ambient (60-800 Hz) | Spread across bass to mid range — rich, layered soundscape | ✓ |
| Full spectrum (50-2000 Hz) | Bass through high-mid — maximum separation | |

**User's choice:** Wide ambient (60-800 Hz)
**Notes:** None

### Register assignment

| Option | Description | Selected |
|--------|-------------|----------|
| Keep as shown | HTTPS at ~175 Hz is low enough for bulk drone feel | ✓ |
| Swap to match prior rule | Strictly follow bulk=low, control=mid, interactive=high | |
| You decide | Let Claude optimize Hz values | |

**User's choice:** Keep as shown
**Notes:** None

### Tuning approach

| Option | Description | Selected |
|--------|-------------|----------|
| Musical intervals | Harmonic/musical relationships so layers blend pleasantly | ✓ |
| Arbitrary spacing | Spread evenly, simpler but may clash | |
| You decide | Claude picks | |

**User's choice:** Musical intervals
**Notes:** None

### Unknown traffic tone

| Option | Description | Selected |
|--------|-------------|----------|
| Single fixed tone at top of range | Always ~800 Hz | |
| Dissonant/detuned tone | Off-key or beating frequency signals unclassified traffic | ✓ |
| You decide | Claude picks | |

**User's choice:** Dissonant/detuned tone
**Notes:** None

---

## Waveform Texture

### Richness

| Option | Description | Selected |
|--------|-------------|----------|
| Pure sine waves | Clean, minimal, ethereal — single frequency per class | |
| Sine + 2-3 harmonics | Fundamental + overtones — warm, pad-like, textured | ✓ |
| Unique waveform per class | Different harmonic profiles per traffic type | |

**User's choice:** Sine + 2-3 harmonics
**Notes:** None

### Harmonic ratios

| Option | Description | Selected |
|--------|-------------|----------|
| Same ratios everywhere | All classes use identical harmonic recipe | |
| Vary per class | Each class gets different harmonic weights for timbral distinction | ✓ |
| You decide | Claude picks | |

**User's choice:** Vary per class
**Notes:** None

---

## Amplitude Dynamics

### Responsiveness

| Option | Description | Selected |
|--------|-------------|----------|
| Slow, glacial (2-4 sec) | Layers swell and fade gradually like weather | |
| Medium (1-2 sec) | Noticeable response, still smooth | ✓ |
| Snappy (0.5-1 sec) | Layers track traffic closely, more reactive | |

**User's choice:** Medium (1-2 sec)
**Notes:** None

### Zero-traffic behavior

| Option | Description | Selected |
|--------|-------------|----------|
| Fade to full silence | Only active traffic produces sound | |
| Fade to a whisper | Barely-audible trace remains for any seen protocol | ✓ |
| You decide | Claude picks | |

**User's choice:** Fade to a whisper
**Notes:** None

### Whisper floor type

| Option | Description | Selected |
|--------|-------------|----------|
| Fixed floor | Once seen, stays at fixed very-low amplitude (2-5%) | ✓ |
| Recency-based decay | Whisper fades further over time based on recency | |
| You decide | Claude picks | |

**User's choice:** Fixed floor
**Notes:** None

---

## Mixing & Headroom

### Mix strategy

| Option | Description | Selected |
|--------|-------------|----------|
| Fixed equal gain | Each layer gets 1/N headroom (~0.09 max) | ✓ |
| Weighted gain by priority | Bulk traffic gets more headroom | |
| Dynamic limiter | No fixed gain, soft-clip if exceeds headroom | |

**User's choice:** Fixed equal gain
**Notes:** None

### Sample rate

| Option | Description | Selected |
|--------|-------------|----------|
| 44100 Hz (CD quality) | Standard, LAME native | ✓ |
| 22050 Hz (half rate) | Smaller files, still fine for <800 Hz | |
| You decide | Claude picks | |

**User's choice:** 44100 Hz
**Notes:** None

### MP3 bitrate

| Option | Description | Selected |
|--------|-------------|----------|
| 128 kbps | Good quality, ~1 MB/min | ✓ |
| 192 kbps | Higher quality, ~1.5 MB/min | |
| You decide | Claude picks | |

**User's choice:** 128 kbps
**Notes:** None

### Channel mode

| Option | Description | Selected |
|--------|-------------|----------|
| Mono | Single channel, simpler | |
| Stereo with panning | Each class panned for spatial separation | ✓ |

**User's choice:** Stereo with panning
**Notes:** None

### Panning approach

| Option | Description | Selected |
|--------|-------------|----------|
| Fixed positions by register | Bass center, mid spread, high wider | ✓ |
| Even spread | All 11 evenly from hard L to hard R | |
| You decide | Claude picks | |

**User's choice:** Fixed positions by register
**Notes:** ICMP center, DNS slight-L, HTTPS slight-R, etc.

---

## Claude's Discretion

- Exact Hz values per class (within 60-800 Hz, musical intervals)
- Specific harmonic ratios per traffic class
- Exact EMA alpha/decay constants for 1-2 sec feel
- Exact whisper floor percentage (2-5%)
- WAV intermediate format usage
- Stereo panning implementation method

## Deferred Ideas

None — discussion stayed within phase scope