Time to Read: 18 minutes
by Pauline Primrose-Heaney
Speech. Noise. Music. Not all sound is created equal; rather, there are many nuances when it comes to what we hear. Or more importantly, how we hear it, because hearing is individual.
So when it comes to addressing hearing loss, hearing aids manufacturers develop technology that can differentiate between speech and other sounds - both the wanted and unwanted background noise.
And as the primary goal of most people who get hearing aids is to improve their speech understanding (in quiet and in noise), manufacturers focus on this as their top priority when developing new technology. In fact, modern digital hearing aids currently do quite a good job of this, and continue to improve all the time.
While many people are satisfied with how their hearing aids work in improving speech understanding, not everyone is happy with how their hearing aids sound when listening to music.
Compared to speech, music is on an entirely different scale of hearing ability. Manufacturers have struggled to develop hearing aids that can clearly hear everything - a huge task, given that the range that encompasses music is so much larger than that of language/speech.
Figure 1. Frequency-intensity range of speech and music within the audibility of the human auditory system.*
Factor in the many different musical instrument timbres, musical genres, live versus recorded music, variations in recording and speakers - these can all affect how music sounds. For instance, the figures below show the frequency-intensity range of speech compared to live music (figure 2), as well as the frequency ranges of various musical instruments and how their fundamental frequency and harmonics contribute to what and how we distinguish them (figure 3).
Figure 2. Frequency-intensity range of speech and live music within the audibility range of the human auditory system. **
Figure 3. Frequency ranges of various musical instruments. The range on the left represents the fundamental frequency which determines the pitch of the note. The transparent colour to the right shows harmonics, which contribute to the perceived sound quality and assist in differentiating different instruments timbres.***
Due to this variability, it’s almost an impossible task to tailor hearing aids to everyone’s individual preferences for music. Rather, manufacturers try to make general improvements by creating a music program that tries to address music in general, regardless of what or how people listen to music, which, as expected, doesn’t satisfy everyone.
When it comes to musicians and audiophiles, it becomes even clearer that setting up hearing aids to optimise speech as well as music requires separate programs. In fact, there may be several music programs required, depending on the specific listening condition.
As mentioned, speech audibility is the main priority of hearing aid manufacturers when developing their technology. The features that help with speech processing (feedback cancellation, noise reduction, compression etc), however, can be the very things that negatively impact music enjoyment.
In fact, some hearing aid wearers prefer older hearing aid technology, even analogue technology, feeling that newer technology filters out too much of the sound when it comes to music. While this older hearing aid technology may help improve music enjoyment, the technology does not improve speech clarity as much as its more modern counterparts.
So let’s take a closer look at some of the technology and sound processing features available in current digital hearing aid technology that can impact (positively or negatively) on music enjoyment:
Bluetooth connectivity and direct streaming
Every manufacturer now offers hearing aid options that are capable of direct streaming via Bluetooth.
This can help with recapturing the nuances and quality of music that can be lost due to listening to sound via a speaker. The speaker quality and room acoustics can affect how music sounds through a hearing aid, so being able to stream the music directly through hearing aids can improve sound quality exponentially.
Phonak Paradise and Marvel currently offer the best music streaming quality. This is owing to the fact that their audio streaming profile detects whether you’re streaming a speech source or a music source and automatically adjusts to optimise the sound. Unitron Discover Next, being a sister company of Phonak, also offers a similar streaming program.
Sound frequency response range
Having a higher frequency response can help music to sound a little fuller. Most manufacturers offer up to around 8 kHz in their hearing aid frequency response range, but there are some, including Widex, ReSound, and Beltone, that offer up to 10 kHz.
It’s also important to keep in mind that the more the severe the hearing loss, the less benefit the wearer will get out of an extended frequency response range as well. More powerful hearing aids that are best suited for these more severe hearing losses tend to limit their frequency response range to around 6.5 kHz as well because of this.
Maximum sound input level
The range of music is much greater than that of speech, so having a hearing aid that offers a high maximum sound input level and large sound input range will improve how it sounds with music (especially live music). A hearing aid that isn’t able to handle higher sound inputs will start to clip and distort once the music becomes louder. Many manufacturers’ hearing aids tend to start distorting from around 106 dB SPL.
Widex offers a sound input range that starts at 5 dB SPL and goes up to 113 dB SPL. ReSound and Beltone also offer a higher maximum output level of 116 dB. This means you can hear all the smaller nuances in soft music as well as enjoy the louder dynamics without sacrificing sound quality.
Processing delay
While it’s impressive that hearing aids can do what they do when processing in noise, all these features mean just that: processing.
The more processing that needs to be done, the more delay in the final sound reaching your eardrums that can occur - some manufacturers have been measured to have a 6-8 millisecond (mS) delay. A fast rate of signal processing results in a lower processing delay which means less distortion, less artificial sound, and fewer artefacts in the signal. Widex offers the lowest processing delay in the industry - 2.5 mS. In their latest Moment hearing aid family, they also offer a PureSound program (best for those with open fittings), where the delay is less than 0.5 mS. Less delay means that the sound quality is cleaner, richer, and fuller.
Feedback Management System
The type of feedback management system a hearing aid employs can definitely have a huge impact on the music sound quality.
Music can incorporate certain tones (consider the flute, for example) that can be confused by the hearing aid as feedback. Traditional feedback systems work to cancel these sounds, and can, actually, introduce feedback if it reacts mistakenly to music as feedback. Sometimes disabling the feedback system for a music program can improve music quality; however, this must be balanced carefully, as there can be a trade-off between hearing aid stability and expected gain.
Feedback systems that are able to switch to analysing the sound input over a longer period of time can be more accurate in distinguishing true feedback from other sounds, such as music.
Starkey, Signia, and Widex offer this flexibility in their feedback system settings. A lot of feedback systems also employ gain reduction as an option for minimising feedback, which can result in a drop in hearing aid volume, which is less than optimal when listening to music. Oticon Opn S utilises 3 different feedback strategies which has shown great results in improving speech understanding as well as some improvements in music sound quality.
Compression
Compression in a hearing aid is not a feature, per se, but part of how it works to amplify sounds for a hearing aid wearer.
Hearing aids tend to be programmed non-linearly. For someone with a hearing loss, we don’t want to increase every sound (from soft to moderate to loud) exactly the same.
We tend to give more emphasis to very soft sounds and moderate sounds, and much less emphasis to loud sounds so that all sounds fit comfortably into the reduced dynamic range of someone with a hearing loss. While this works well for speech, it can completely backfire on music. Music tends to require hearing aids to be set more linearly. As an audiologist, being able to adjust the compression ratios in a hearing aid can be crucial for improving music sound quality for the hearing aid wearer.
Frequency lowering
Frequency lowering and music can be hit and miss. Some people can’t stand it, while others prefer it.
The hearing loss configuration can play a big part in this, as frequency lowering balances audibility (with it switched on) and sound quality (with it switched off). Most manufacturers offer some form of frequency lowering or frequency compression, and this is a setting for the audiologist, rather than the end user, to adjust.
Music programs dedicated to different music listening requirements
All manufacturers offer a dedicated music program option which will have pre-calculations that are set to reduce the impact of the feedback manager on music, disable all adaptive features, adjust the compression, and set the sound output to maximum for less distortion.
Some manufacturers like Unitron also allow the audiologist to select the music genre which pre-calculates the frequency response that may best suit it. Signia X likewise offers 3 music program settings for full music appreciation - one for listening to recorded music, one for live music at concerns, and one specifically for musicians and singers performing music.
That being said, these settings are just a starting point, as they are still generic programs, so can still take some adjusting to suit individual listening preferences (the same can be said for fitting and adjusting a hearing aid for speech).
In my own experience with adjusting hearing aids to optimise music enjoyment, I’ve found that definitely adding at least one separate music program works best, as what works for speech doesn’t work for music and vice versa.
As a rule of thumb, hearing aid manufacturers I’ve found that have tended to work best for music over the years are Widex and ReSound (and now Beltone as they offer the same hearing aid range), although the newer Phonak (from Marvel onwards) seems to have improved for music as well (although Phonak doesn’t quite offer the same extended sound input range so can still be slightly less natural for music compared to Widex and ReSound/Beltone).
Certainly the music streaming sound quality with Phonak is superior to any of the made for iPhone hearing aids on the market. However, as hearing is individual, it’s best to have the opportunity to be able to trial a couple of options to see what works best for you - often, it’s about finding a good balance between speech audibility and music enjoyment. Flexibility and patience is the key when it comes to finding the best hearing aid for a hearing impaired individual with specific music sound quality goals.
As you can see, programming a hearing aid to optimise music enjoyment is not that straight-forward. It involves the active participation of the hearing aid wearer.
For musicians, being able to play your instrument, utilising its full frequency and dynamic range, while having your hearing aid adjusted is important. Fortunately, the introduction of teleaudiology and remote hearing aid adjustments has made this easier than ever, as it also allows for hearing aids to be adjusted while playing a musical instrument in the same acoustic environment that the wearer may typically practise in.
For those who enjoy listening to, rather than playing, music, having your audiologist play your favourite piece of music while adjusting your hearing aid settings and providing feedback on the sound quality can be useful.
Likewise, remote adjustments can be employed for adjusting hearing aids while listening to recorded music on your own sound system. Also be mindful that despite the features mentioned above, there might still be some limitations, especially for notes in the lower frequency range.
Some of these may be addressed by your audiologist changing the acoustic coupling (dome type, mould vent, mould canal depth) on your hearing aid. Be prepared to work with your audiologist in finding a hearing aid and a setting (or settings) that works well for your music listening needs - the results can certainly be very rewarding.
* Limb, C (2011, October). Building the musical muscle [Video file].
** DePaolis, R. A., Janota, C.P., & Frank, T. Frequency Importance Functions for Words, Sentences, and Continuous Discourse. Journal of Speech, Language, and Hearing Research, 39(4), 714-723.
*** O’Brien, I., Driscoll, T., & Ackermann, B. (2013). Sound exposure of professional orchestral musicians during solitary practice. The Journal of the Acoustical Society of America, 134(4), 2748-2754.
