Knowles Corporation, a provider of advanced micro-acoustic microphones and speakers, audio solutions and high-performance capacitors and RF products, today releases research demonstrating a new Preferred Listening Response Curve for earphone design, reflecting findings to ensure a music listening experience for consumers.
Sound quality continues to be at the top of the list for consumer audio demand, yet many True Wireless Stereo (TWS) earphone manufacturers have been slow to take advantage of the developing hi-res audio ecosystem. With the proliferation of lossless music streaming subscription services like Tidal, Amazon Music HD and Apple Lossless, together with availability of high data rate Bluetooth codecs, the industry is able to deliver hi-res audio wirelessly with the right hardware and tuning. Knowles’ latest research provides valuable insight into how to satisfy consumer demand for the best-sounding audio in either wired or wireless earphones.
Knowles analyzed more than 200 recordings, chosen from the last 20 years of the Billboard Hot 100 to represent much of the music that headphone wearers are likely to be streaming. This revealed significant high-frequency content above 10 kHz in popular music that many earphones fail to reproduce well. From here, the team conducted controlled blind testing of a wide variety of listeners – with a range of demographics and hearing abilities – to determine what makes the best sound quality, as preferred by listeners.
Optimum high-frequency response is key when designing hi-res earphones. Using technology only recently available, Knowles was able to extend an understanding of user preference beyond 10 kHz to create the new Knowles Preferred Listening Response Curve. By focusing on the high frequency response, the new curve is uniquely suited to give manufacturers the insight needed to deliver the best hi-res listening experience.
Key findings from the Knowles research shows that earphones tuned to earlier concepts of what sounds good severely understate the amount of high-frequency energy that listeners prefer. According to the Knowles Preferred Listening Response Curve, listeners consistently preferred between 12 and 21 decibels (dB) of boost at frequencies beyond 10 kHz, depending on age and hearing ability. Designing and tuning an earphone that matches the high-frequency boost identified using the Knowles Preferred Listening Response Curve is expected to consistently provide a highly satisfactory end-user experience and receive high ratings from consumers.
The Knowles Curve is also a tool when used with hearing personalization algorithms. Knowles included subjects with various levels of reduced high-frequency hearing response and determined their preferred amount of boost. With this data, designers of TWS earphones with hearing personalization can configure their algorithm to produce the optimum sound quality across the range of hearing abilities commonly experienced by consumers.
“Consumers want hi-res, premium sound through their TWS earphones. This has been a challenge for OEMs who have had no clear guideline for what consumers prefer across the full spectrum. Now we know exactly how to design and tune a TWS earphone to create the best sounding audio available,” said Shehab Albahri, Sr. Director of Knowles Hearing Health Technologies R&D. “Brands that design with hi-res capable hardware and tune their earphones to the Knowles Curve will unlock the true potential of lossless streaming audio.”