Factors that Influence Listeners’ Preferred Bass and Treble Levels in Headphones

Most people would agree that headphone purchase decisions are heavily influenced by the brand and styling (size,  weight, color, quality of  materials).   But what is considered stylish and fashionable  by me is not shared by my 15-year old daughter (this week donning purple hair), and vice versa. In other words, the perceived visual aesthetic  of the headphone  is really in the the eyes and mind of the beholder, and this can vary with age, gender, culture, and other demographic category. 

But what about sound quality?  To what extent does the consumer's  age, gender, culture and prior listening experience influence their taste in headphone sound quality?  Is there a scientific basis for headphone manufacturers to design headphones that have different amounts of bass and treble aimed to satisfy the tastes of a targeted demographic group? 

To answer this question, we recently conducted a  study on factors that influence listeners’ preferred bass and treble balance in headphone sound reproduction. Using a method of adjustment a total of 249 listeners adjusted the relative treble and bass levels of a headphone that was first equalized at the eardrum reference point (DRP) to match the in-room steady-state response of a reference loudspeaker in a reference listening room. Listeners repeated the adjustment five times using three stereo music programs. The listeners included males and females from different age groups, listening experiences, and nationalities (Canada, USA, Germany and China).  The results provide evidence that the preferred bass and treble balances in headphones was influenced by several factors including program, and the listeners’ age, gender, and prior listening experience. The younger and less experienced listeners on average preferred more bass and treble in their headphones compared to the older, more experienced listeners. Female listeners on average preferred about 1 dB bass and 2 dB treble than their male counterparts. Listeners over 55 years preferred less bass and more treble than the younger listeners suggested that they were compensating for possible hearing loss that is associated with increased age.

We recently presented the results of this study at the 139th Audio Engineering Society Convention in New York City, October 29th-November 1, 2015. The paper is available for download in AES e-library. A PDF copy of the presentation can be found here. Or you can view an animated version of the presentation on Youtube.

My Article on Headphone Sound Quality in 2014 LIS

The 2014 Loudspeaker Industry Sourcebook came out this week. In it, you can find an article I wrote called "Perceiving and Measuring Headphone Sound Quality: Do Listeners Agree on What Makes a Headphone Sound Good?"

The article is a summary of some recent published research we've conducted at Harman on the perception and measurement of headphone sound quality.

Together, these studies provide scientific evidence that when headphone brand, price, fashion, and celebrity endorsement are removed subjective evaluations, listeners generally agree on what makes a headphone sound good.

So far, this has been true regardless of users' listening training, age, or culture.  The more preferred headphones tend to have a smooth, extended frequency response that approximates an accurate loudspeaker's in-room response. This new target frequency response could provide the basis for a new and improved headphone target response. You can find more details on the research here.

The Science and Marketing of Sound Quality

To my surprise, this morning an audio friend tweeted a link to an article I recently wrote for our company's  internal newsletter  entitled, "The Science and Marketing of Sound Quality."  My article can be found on a new Harman Innovation website  launched today that features articles on current and future disruptive technology that will impact consumers' infotainment experiences. Check it out.

My article focuses on a longstanding pet peeve of mine (first mentioned in this blog posting): The lack of  perceptually meaningful loudspeaker and headphone specifications in our industry.  While consumer surveys repeatedly report sound quality to be a driving factor in their audio equipment purchases, consumers lack the necessary tools and information to identify the good sounding products from the duds.

This is particularly true for loudspeakers and headphones where the typical throw-away "10 Hz to 40 kHz" specification provided by the manufacturer is utterly useless. This specification only guarantees that the product makes sound, with no guarantee that the sound is good.  While the science exists today to accurately quantify and predict the perceived the sound quality of  loudspeakers (and hopefully, soon headphones), the audio industry continues to drag its heels into the 21st century,  and not routinely provide this information to consumers.

A rare exception is JBL Professional who provides comprehensive detailed measurements on studio/broadcast monitors like the new JBL M2 Master Reference shown below. Inspecting the measured frequency response curves shown  below, you can easily recognize the loudspeaker sounds exceptionally neutral and accurate based on the shape (flat, smooth, and extended)  Based on this set of measurements, we can predict how a listener would rate the sound quality of the loudspeaker in a controlled listening test, with 86% accuracy. The only pertinent information not shown in this graph is how loud the loudspeaker will play before producing audible distortion (trust me, this loudspeaker will play very loud! )

Perceptually meaningful loudspeaker specifications like these have been available for almost 30 years! Yet,  these specifications are currently not part of any professional and consumer loudspeaker standard. Such a standard would go a long way towards improving the quality and consistency of recorded and reproduced sound. Audio consumers want to hear the truth. We need to provide better information and audio specifications so they can find it.

JBL M2 Master Reference Monitor provides true reference sound quality that is clearly indicated by its technical measurements shown below. 

The spatially-averaged frequency response curves of the JBL M2  (from top to bottom) for the listening window (green), the first reflections (red), and the total radiated sound power.  At the bottom are shown directivity indices of the sound power (dotted blue) and first reflections (dotted red). These measurements tell us that the quality of the direct and reflected sounds produced by the loudspeaker will be very accurate and neutral over a relatively wide listening area.

More Evidence that Kids (American and Japanese) Prefer Accurate Sound Reproduction

Geoffrey Morrison, an audio writer at CNET and Sound & Vision has posted a nice summary  of my latest AES paper "Some New Evidence that Teenager and College Students May Prefer Accurate Sound Reproduction" presented at the recent  132nd AES Convention in Budapest, Hungary.


The paper is available for download here at the  AES E-library, and I have provided a YouTube video and a PDF of my presentation slides that summarize the main points of the research.


 The abstract of the paper reads as follows:


A group of 58  high school and college students with different expertise in sound evaluation participated in two separate controlled listening tests that measured their preference choices between music reproduced in (1) MP3 (128 kbp/s) and lossless CD-quality file formats, and (2) music reproduced through four different consumer loudspeakers. As a group, the students preferred the CD-quality reproduction in 70% of the trials and preferred music reproduced through the most accurate, neutral loudspeaker. Critical listening experience was a significant factor in the listeners’ performance and preferences. Together, these tests provide some new evidence that both teenagers and college students can discern and appreciate a better quality of reproduced sound when given the opportunity to directly compare it against lower quality options. 


The effects of culture and trained versus untrained listeners on loudspeaker preference are topics that have been discussed in previous postings on Audio Musings. To further shed some light on this topic, I also ran 149  native speaking Japanese college students through the same loudspeaker preference test along with 12 Harman trained listeners.  The graph below shows the mean loudspeaker preference ratings for these two groups of listeners along with the four different groups of high school and college students from Los Angeles.  

Not surprising, (at least to me) I found that the Japanese college students on average preferred the same accurate loudspeaker (A) as did the 58  Los Angeles students, and the trained Harman listening panel. The main differences among the different listening groups  were related to the effect of prior critical listening experience:  the more trained listeners simply rated the loudspeakers lower on the preference scale, and were more discriminating and consistent in their responses. This result is consistent with previous studies. The least preferred and least accurate loudspeaker (Loudspeaker D) generated the most variance in ratings among the different listening groups. This  was explained by its highly directional behavior combined with its inconsistent frequency response as you move from on-axis to off-axis seating positions. This meant that listeners sitting off-axis heard a much different (and apparently better quality) sound than those listeners  sitting on-axis.


 While the small sample size of listeners doesn't allow us to make generalizations to larger populations, nonetheless it is reassuring  to find that  both the American and Japanese students, regardless of their critical listening experience, recognized good sound when they heard it, and preferred it to the lower quality options.


It would appear that the reason kids don't own better sounding audio solutions has nothing to do with their supposed "deviant"  tastes in sound quality, but more do with  other factors  (e.g. price, convenience, portability, marketing, fashion) that have nothing to do with sound quality.  Music and audio companies should take notice that kids can indeed discriminate between good and bad sound, and prefer accurate sound, despite what the media has been falsely reporting for the last few years. With that out of the way, we should focus on figuring out how to sell sound quality to kids at affordable prices and form factors  they desire to own.


The research suggests that if we cannot figure out how to sell better sound to kids, we have no one to blame but ourselves. 

Harman Debunks Youthful Music Myths

Robert Archer, a writer at CEPro magazine has written a nice article called "Harman Debunks Youthful Music Myths." The article is based on an interview he did with me a couple of weeks ago, and summarizes some recent Harman research on Generation Y's sound quality preferences for different digital music file formats (MP3 versus CD) and loudspeakers. The details of the preliminary research were first reported back in June in a blog posting, "Some New Evidence that Generation Y May Prefer Accurate Sound Reproduction."

The early results of that research suggest that today's youth prefer higher quality music formats and accurate loudspeakers when given the opportunity to A/B them under controlled, double-blind listening conditions. While it is refreshing news that good sound is not lost on today's youth, the challenge is to figure out how to market and sell it to them.

Unfortunately, good A/B audio demonstrations are becoming nearly extinct. Internet and Big Box store sales of audio equipment and music generally don't provide such listening opportunities. In the end, consumer education, meaningful audio specifications and measurements that are indicative of a product's true sound quality, and accurate, unbiased product reviews, will help consumers make more informed audio and music purchase decisions as they relate to sound quality. Until then, most consumers will never know for sure whether or not they've purchased something that is truly "good enough."