Page 66 - Spring2022

HEADPHONE SOUND QUALITY
The Harman target curve is one example that is preferred by a majority (64%) of listeners from a broad range of ages, listening experiences, and genders. Slight adjustments in the bass and treble levels may be necessary to compensate for variance in the quality of recordings and to satisfy indi- vidual tastes. The Less Bass Is Better class (21% of listeners) includes a disproportionate percentage of females and older listeners and none of the trained listeners. The More Bass Is Better class is skewed toward males versus females by a factor of 4 to 1. There is no evidence that sound qual- ity preferences are geographically influenced. Recognition of good sound reproduction seems to be universal.
Objective measurements of the headphones using stan- dard ear simulators can predict how good they sound. The further the frequency response a headphone deviates
from the Harman target response, the lower its perceived sound quality will be. A simple linear model based on these deviations can predict how listeners would rate it in controlled listening tests.
The reaction from the headphone industry to this new research has been largely positive. There is evidence that the Harman target curve is widely influencing the design, testing, and review of many headphones from multiple manufacturers, providing a much needed new reference or benchmark for testing and evaluating headphones. Several headphone review sites provide frequency response measurements of headphones show- ing the extent to which they comply with the Harman target (Vafaei, 2018; Audio Science Review, 2020); in cases where they fall short, corrective equalizations are often provided.
As expected, there are also critics whose headphone tastes in sound may not agree with the research. The Harman target is intended as a guideline and is not the last word on what makes a headphone sound good. One legitimate criticism is the limited number of headphones, programs, female listeners tested, and questions raised about the confluence of variables like hearing loss and its effect on headphone preference. Future studies will hopefully address this. Finally, I hope that this article encourages others to continue the research and improve our knowl- edge of the perception and measurement of headphone sound quality. Although listeners largely agree on what makes a headphone sound good, there are still many unanswered questions and more to learn.
References
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66 Acoustics Today • Spring 2022