# Lab 1: Critical Listening in a 3D Spatial Audio Engine

> Train your ears like a pro. Use a five-pass listening protocol in the live Spatial9 3D audio engine and map position, width, height and distance.

Web page: https://spatial9.ai/blog/academy-lab-critical-listening
Author: Spatial9 Team
Published: 2026-10-04. Updated: 2026-10-16.

## Key takeaways
- The five-pass protocol covers the whole mix, solo layers, an A/B of 3D positioning on and off, a format switch, and head tracking.
- Listen on headphones in a quiet room at one moderate, fixed level, and rest your ears in silence every 20 to 30 minutes.
- Eight terms describe space precisely: position, width, height, distance, movement, envelopment, clarity and masking.
- Position can be recorded on a clock face where 12 is straight ahead, 3 is right, 6 is behind and 9 is left.

In this lesson: You will run a structured, five-pass listening session in the live Spatial9 3D Spatial Audio Engine. You will learn a shared vocabulary for describing space, fill in a listening worksheet, and draw a top-down map of where 23 stems live around your head.

Every great immersive engineer has the same secret weapon. It is not a plugin, a speaker array or a faster computer. It is a trained pair of ears and a disciplined way of using them.

Critical listening is a skill, and like any skill it grows with practice. The difference between a beginner and a professional is rarely that the professional hears more. It is that the professional knows what to listen for, listens in a repeatable order, and writes down what they hear.

In the previous lessons you learned how the brain hears in 3D, how formats describe space, and how spatial inference lets GravityLLM propose where sounds should live. Now it is your turn. This is the first of three capstone labs in Spatial9 Academy, and it gives you the listening method you will use in every lab that follows.


## What you will learn

- How to prepare your body, your room and your headphones for a reliable listening session.
- A five-pass protocol that moves from the whole mix to single layers, A/B comparisons, formats and head tracking.
- Eight words that professionals use to describe space: position, width, height, distance, movement, envelopment, clarity and masking.
- How to fill in a listening worksheet and draw a top-down listening map.
- Why personal hearing differences matter, and how the Hearing Accessibility profile helps.

The rest of this lesson is free with a Spatial9 account: https://spatial9.ai/blog/academy-lab-critical-listening