After posting the findings from our recent expert-analysis of the Soundhawk (Part I and Part II), we received a few extremely enlightening emails from the company’s Chief Scientific Officer, Drew Dundas, PhD. We asked Dr Dundas if we’d be able to post some of his responses here on Hearing Tracker. He agreed to share some of his thoughts publicly, and consolidated his thoughts into the following text. All questions and comments should be left in the comment section, at the bottom of this post.
Dear Dr. Bailey,
Thank you again for your in-depth and insightful review of the Soundhawk Smart Listening System. As you noted in your comprehensive review, Soundhawk was founded to bring enhanced listening performance and increased ease of listening to a wider range of individuals. Our team is unique in the hearing space, bringing together hearing experts with innovators from the consumer electronics world. Our founder, Dr. Rodney Perkins, is the founder of ReSound, a well-known otologist and professor of surgery at Stanford University who has been a champion for improved hearing health throughout his extensive career.
During my time as a Director of Audiology at UCSF Medical Center and as a clinician at Vanderbilt University Medical Center I was frequently struck by the obvious need for a high quality, high technology product that is intended for use by individuals with situational listening difficulty.
What is situational listening difficulty?
Many of your readers have probably heard or even described for themselves the experience where the listener doesn’t have any difficulty following a conversation with a friend in their own living room, but if that conversation were to move to a noisy restaurant, it becomes a whole new ball game. In fact, a study published in late 2014 by the Consumer Electronics Association reported that as many as 98 million adults in the United States report difficulty listening and understanding in common situations. That’s almost half of the adults in the US.
For a number of reasons, the majority of these individuals aren’t candidates for care through the traditional Audiology channel, including the fact that many of these individuals likely have hearing sensitivity (i.e., audiometric test results) well within the normal range. For these individuals, improving the audibility of the speech signal (what we tend to think of as ‘making things louder’) is of secondary importance to improving the signal to noise ratio. The term signal to noise ratio, of course, refers to the relative presence of the things that you want to hear (the signal) versus the presence of the things that you’d like to ignore (the noise). Soundhawk is the first and only consumer product that is intended to enhance listening performance and ease by focusing on personalization of sound and enhancement of the signal to noise ratio.
In your review of the Soundhawk Smart Listening System, it is astutely observed that Soundhawk enhances key speech frequencies via careful manipulation of the sound signal. Unlike hearing aids, which are intended to compensate for a loss of hearing, Soundhawk’s processing is intended to enhance the hearing performance that exists. There are no compromises for the user. Our personalization system allows the user to simultaneously manipulate more than 150 different parameters with a simple drag of their finger through our patented personalization app on a smartphone or tablet. These changes are much more complex than a bass/treble and volume control. Because listening conditions change, the Soundhawk user can readjust their settings as often as they’d like, simply by returning to the Soundhawk App.
During the test box evaluation of Soundhawk, the reviewers observed a more robust directional response in the indoor mode than in the dining mode and question the reasoning behind this performance. It would appear that these results are an artifact of the test protocol, rather than a flaw in the implementation of the directionality system. In the Indoor sound scene, Soundhawk utilizes a fully automatic adaptive directional microphone mode. That is, when there is very little background noise, the microphone response pattern is omnidirectional, lowering the system noise floor and improving sound quality. When background noise is detected, the system goes into a ‘search and destroy’ mode, reassessing the signal to noise ratio hundreds of times each second and adapting the microphone response pattern to maximize the SNR in front of the user.
We selected an automatic adaptive strategy for this mode because we know that most competing noise at home is stationary, such as what might be produced by home ventilation, an adjacent kitchen or traffic noise through an open window. In addition, many users prefer a baseline setting that is highly versatile and effective. The Audioscan Verifit directional test utilizes a test stimulus containing speech or noise that is presented from speakers in front of and at 90 degrees to the microphone array. Because the Verifit noise source is at 90 degrees from the signal, the automatic adaptive directional mode of the indoor setting is able to adopt a response pattern that is less sensitive to sound emanating from this direction. In the dining mode, on the other hand, we force the system into a fixed directional response pattern that is more sensitive to sounds coming from the front and just to the sides, the presumed location of dining companions and conversational partners. We chose this setting because of the highly variable acoustic environment of a restaurant. A quickly adapting response would result in major fluctuations of the level of sound, an effect that is distracting to many listeners.
It was gratifying to see that the noise reduction system of the Smart Listening System worked well in the test box in driving mode. Use of the vacuum cleaner and air conditioner sound effects was creative, but may have underestimated the efficacy of the system for road noise and wind, sounds that are more typically encountered when driving than is vacuum cleaner noise.
The assessment of the wireless microphone performance was impressive. The reviewer’s recordings did an excellent job of illustrating the effect of the system on ease of listening in background noise. As audiologists have advocated for decades, wireless microphones massively enhance the signal to noise ratio for all listeners, making understanding in noise much easier and less tiring. Until Soundhawk, however, this wireless technology has not been available at a price point that is easily accessible for most people.
Soundhawk is unilateral in design because individuals with situational listening difficulty can derive greater benefit in noise from signal to noise ratio improvement than from amplification. A unilateral design is simple, versatile (it doubles as an excellent Bluetooth headset for use with your smartphone!), effective and affordable. While the ‘perfect’ fit might not be achieved by a user without the assistance of a professional, one really has to ask what ‘perfect’ means. The audiogram based fitting targets described by the reviewer are averages based on one aspect of hearing only: the softest sounds detectable by the listener. While this approach has been well validated to provide benefit in terms of enhanced audibility for speech, it is more difficult to say that they predict user satisfaction. In fact, the literature suggests that while these targets serve as an excellent starting place, they should not be considered the ‘final destination’. The scientists who developed the NAL-NL1 fitting target algorithm also published a paper that pointed out the fact that different listeners might prefer settings that varied from the audiogram-based prescription by as much as 20dB, reaffirming that the fitting target should be considered no more than a starting place for a satisfied user.
The reviewers note that when the Soundhawk system is operated at maximum volume and maximum boost in a noisy situation, that sound quality may degrade somewhat. This does not occur because of a hardware limitation, but rather due to our careful setting of the maximum output parameters of the system. We consider it our responsibility to ensure that it is never possible to produce an output level that would be hazardous to the hearing of the user. Accordingly, we carefully tailor the gain, compression ratios and output limiter settings such that output is maintained in the safe range. If the user encounters distortion or other degradations in sound quality when listening in noisy situations, it is recommended that the volume control level be decreased until sound quality improves.
Lastly, the reviewers question ‘who is Soundhawk for?’
Soundhawk has developed a simple test to determine who might benefit from the use of the Smart Listening System. In essence, If you experience little to no difficulty listening to conversation in a quiet room, but struggle in background noise, or when listening to the television with others, Soundhawk will likely help you to listen with less difficulty and less effort. If, on the other hand, you experience difficulty listening and understanding in quiet, you would likely perceive greater benefit from professional evaluation and treatment. To learn more, visit http://www.soundhawk.com/#right-for-me
We at Soundhawk appreciate the interest, thought and obvious expertise that went into the Hearing Tracker review of the Smart Listening System. As always, we recommend that everyone should have their hearing evaluated by an audiologist or hearing healthcare professional, and carefully compare the features and benefits of the various approaches to improving situational listening performance before making a decision on how to go about improving their ease of listening and quality of life. Potential users with medical symptoms including sudden changes in hearing, tinnitus, dizziness, ear pain or drainage should consult their healthcare provider prior to using Soundhawk or any other hearing related products.
For more information, please visit www.soundhawk.com
Drew Dundas, PhD, FAAA
Chief Scientific Officer
Last modified: March 17, 2015