Why Do We Have Two Ears but Test with One Mic?

In the latest Bulletin (March/April 2026), there is an interesting article, “Why do we have two ears but test with one mic?” by Mark Dowie MIOA, Noise & Vibration Applications Specialist at HEAD acoustics.

It explores a question many of us in acoustics may have considered: if human hearing is inherently binaural, why do so many traditional measurement approaches rely on a single microphone? The article introduces Head and Torso Simulators (HATS) as a more representative way of capturing how we truly experience sound.

Dowie provides a fascinating overview of how HATS technology has evolved—from its origins in hearing aid testing with KEMAR in the 1970s, through to its widespread adoption across industries including telecommunications, automotive NVH, and consumer audio. A key takeaway is the importance of acoustic impedance and why realistic ear simulation is critical for accurate and repeatable measurements, particularly for devices like headphones and hearing aids.

The article also highlights the role of binaural recording and head-related transfer functions (HRTFs) in enabling immersive, spatial audio experiences. By replicating the subtle effects of head shadow, time delay, and the geometry of the outer ear, HATS allow engineers to capture sound in a way that closely matches human perception.

Looking ahead, the piece touches on exciting developments such as digital twins and the growing importance of HATS in electric vehicle design, where the absence of engine noise makes previously masked sounds far more noticeable.

You can read more here