Nick Zacharov on Psychoacoustics and the Sounds of Progress
John Ennis
Contributor
Executive Summary
In this in-depth interview, John Ennis sits down with Nick Zacharov, a leading expert in psychoacoustics and sound engineering. Nick shares his journey from a music-loving teenager to a renowned acoustician, detailing his foundational education in the Tonmeister program, his influential work at DELTA SenseLab in Denmark, and his current role driving innovation at Genelec. The conversation explores the critical link between objective audio measurements and subjective human perception, the evolution of immersive audio, and the standardized methodologies that ensure consistent sound quality evaluation across the industry.
Key insights:
- The Importance of Psychoacoustics: True sound quality cannot be determined by physical measurements alone. Understanding human perception through subjective listening tests is essential for designing audio products that deliver a genuinely pleasing and accurate experience.
- Standardization in Listening Tests: Developing and adhering to standardized methodologies, such as those from the International Telecommunication Union (ITU), is crucial for creating reliable, repeatable, and comparable data on sound quality across different labs and products.
- The Challenge of Immersive Audio: Creating a convincing spatial audio experience is a complex challenge that goes beyond simply adding more speakers. It involves understanding how the brain processes spatial cues and overcoming the limitations of both hardware and recording techniques to create a seamless auditory illusion.
- Evolution of Audio Technology: The industry has progressed from basic stereo to complex multi-channel and now to object-based immersive audio systems, driven by a continuous quest for greater realism and a deeper understanding of human hearing.
Full Transcript
From Early Passion to a Career in Acoustics
John Ennis: What is your origin story? What gets you into sound?
Nick Zacharov: That's a long story. It starts back in my teenage years in the UK. I was very much into music. I was in a band, and I got to the point where I got a bit frustrated by playing in a band; I wanted to understand how to record it. So I got into recording. That led me, via a very nice teacher at my school, to do a course called the Tonmeister course at the University of Surrey. There I spent four years studying sound recording and acoustics. That was a fantastic course, and I really enjoyed my time there. I became more and more interested in the perception of sound—why things sound the way they do. In my third year, I had a placement at Bang & Olufsen in Denmark. I came across some people who were very inspirational, and they were really delving into the whys and hows of sound. That led me to stay on in Denmark after my bachelor's degree. I started a PhD at the Acoustics Lab in Denmark, at Aalborg University, with some of the same people I'd met at B&O. There, I really got deep into psychoacoustics. My thesis was about the perception of spatial audio. I did that for three years and then continued for some years as a researcher at Aalborg University.
Pioneering Psychoacoustics at DELTA SenseLab
John Ennis: Tell me about DELTA SenseLab.
Nick Zacharov: DELTA SenseLab is a part of DELTA, which is an organisation in Denmark, a so-called authorised technological service institute. Its goal is to bring high-level research from universities into industry. I joined a team there that became DELTA SenseLab. We were a group of people focused on the subjective evaluation of sound and, later, other modalities. Our work was primarily consultancy and product development for a whole range of industries, from mobile phones and headsets to hearing aids, automotive, and traditional pro audio and hi-fi. We worked with companies to help them understand how their products sound, what their quality is, and how they could improve it. This was based on a philosophy of using human listeners as the ultimate measurement tool. My background at university was in psychoacoustics and listening tests, and we applied that in an industrial context. We had a large listening panel of trained listeners and a suite of acoustically specified listening rooms where we could do our work.
John Ennis: Could you give an example of a typical project?
Nick Zacharov: Let's take a mobile phone. A company wants to develop a new phone and ensure it has a certain level of audio quality. They might ask us to evaluate it against competitor products or a previous generation. We would design a listening test, which involves selecting the appropriate listeners, program material (like speech, music, or ringtones), and a suitable environment. We would choose a methodology for the evaluation, often from a body of standards from the ITU (International Telecommunication Union), which provides recommendations for how to test audio systems. Then we run the experiment, gather the data, perform statistical analysis, and report back to the customer on how their product performs, what its strengths and weaknesses are, and how it's perceived by listeners. It's about bringing the voice of the end-user into the product development cycle in a controlled, scientific, and repeatable way.
The Science of Listening: ITU Standards and Sound Quality
John Ennis: And you helped write some of those ITU recommendations?
Nick Zacharov: Yes, I've been involved in the ITU for over 20 years. I became a member during my PhD and have been active in a number of working parties and study groups that deal with audio quality. I've been involved in writing and editing many of the recommendations for subjective test methods. The value of these international standards is that if I do a test in my lab in Denmark and you do a test in your lab in the US using the same methodology, we should get the same result within statistical limits. It provides a common language and a common yardstick for quality evaluation.
John Ennis: So it's the scientific method applied to listening?
Nick Zacharov: Exactly. In the early days, listening tests were often seen as a black art. Someone would say, "Let's get Dave from down the corridor; he's got golden ears." But that's not a very reliable or robust way to do things. The work we and others have done is to make it a science, to make it an engineering tool that is reliable and repeatable, providing valid results that you can base million-dollar decisions on.
Joining Genelec and the Evolution of Immersive Audio
John Ennis: What prompted the move to Genelec?
Nick Zacharov: I worked at DELTA for about 15 years and had a fantastic time with a great team. But I got an offer from Genelec, a company I had admired for many years. It was an opportunity to work on the other side—not as a consultant, but inside a company, helping to develop products. Genelec has a very strong R&D focus, a fantastic team of people, and a real commitment to quality. The move allowed me to apply my knowledge in a different way, focusing on loudspeaker development and performance. My current title is Senior Research and Development Scientist, and I work on a broad range of topics, including loudspeaker design, system calibration, and our GLM (Genelec Loudspeaker Manager) software.
John Ennis: You've spent a lot of time on immersive audio. What is the state of immersive audio today?
Nick Zacharov: Immersive audio is a very exciting and fast-moving field. My PhD was on spatial audio, and back then, we were just moving from stereo to 5.1 surround sound. Today, we have much more complex systems with many more channels, height information, and object-based audio. The goal is to create a more compelling and realistic sense of space and envelopment. We're seeing this in cinema, home theatre, gaming, and increasingly in music production. However, there are still many challenges. How do you capture an immersive sound field effectively? How do you reproduce it over a limited number of loudspeakers? How do we ensure a consistent experience for all listeners? These are active areas of research. At Genelec, we're providing the tools—the loudspeakers and calibration systems—to allow content creators to work effectively in these new immersive formats.
John Ennis: What is the immersive dream? What are we trying to achieve?
Nick Zacharov: The ultimate dream is what's often called the 'holodeck'—a perfect illusion of being in a different acoustic space. We are still some way from that. We're getting better at creating plausible illusions, but there are still artifacts and limitations. One of the biggest challenges is that our brains are incredibly good at detecting when something isn't quite right. We use a multitude of cues to perceive space—timing differences, level differences, spectral changes, and reflections. Reproducing all of these perfectly for every listener in a room is extremely difficult. But the progress is tangible. The difference between a good immersive mix and a standard stereo mix can be breathtaking.
The Future of Audio Perception
John Ennis: So what's the next five to ten years for you and for sound?
Nick Zacharov: I think we'll continue to see the evolution of immersive audio, with more content becoming available and the tools getting better. Another big area is personalization. With headphones, we have the potential to create a highly individualized audio experience that adapts to your specific anatomy and location. This involves measuring how your ears and head shape the sound, known as the Head-Related Transfer Function (HRTF), and then using that data to create a truly personal binaural experience. We'll also see audio becoming more intelligent and context-aware, adapting to your environment and activity. The fundamental research into perception will continue to be vital. The more we understand about how we hear, the better we can design audio systems that delight and inform us. It's about bridging that gap between the physical world of sound waves and the perceptual world of what we actually experience.