Lightspeed Delta Zulu

FROM £1,195 www.lightspeedaviation.com

It’s always interesting when an active noise reducing (ANR) headset comes on the market, leading to hopes rising of finally overcoming the distraction and discomfort of noise in our aircraft. Last autumn

Lightspeed launched its newest headset, Delta Zulu (DZ). It is the first of a line that Lightspeed calls safety wearables which features CO (carbon monoxide) detection alerts built into the unit. They also included another less heralded, but to me much more important feature, HearingEQuity, which is intended to improve speech clarity beyond that achieved by ANR, through customising the response of the headphones to individual hearing. Ed the Editor managed to acquire a set and asked me to review it.

What I bring to the party is ‘age related’ hearing loss, which, DZ claims, it can alleviate. But before digging out the measuring tools, I flew with it to see if I could detect any significant difference – with most top of the range headsets I can’t. I used the Bluetooth connected app to set DZ up for my ears, presented it with a challenging scenario (a female co-pilot in my noisy RV-6), removed

01 Delta Zulu is similar in feel and appearance to its Zulu predecessors, but is 20% lighter. It’s the internals that have changed dramatically.

Graph of hearing loss vs age

my hearing aids (which I sometimes wear while flying) and went off for a flight wearing Delta Zulu. The result surprised me with excellent reduction of noise and improvement of clarity of communications, even without my hearing aids.

This is a product that should be taken seriously.

How does DZ work? It has good ANR but, in addition, to use its native (USA) vernacular, it is leveraging the fact that most older people (as pilots often are) suffer hearing loss to some extent. Nothing sinister in that, just the normal reduction in high frequency sensitivity that occurs naturally with age (image 2 and also see sidebar, Human ears and aviation pg 42).

DZ’s HearingEQuity feature is electronically applying some correction for this reduction using something akin to an audio graphic equaliser (EQ is the techno shorthand for one). Hi-fi and hearing aids have been using this for decades, but this is the first audio optimisation that has been included in an RT / coms function of an aviation headset. This correction makes any tones, to which your hearing doesn’t respond to so well, louder (typically high ones, see note 1), consequently applying some correction for aging or other hearing deficiency. As no two ears are the same, it can optimise itself for the individual. The first task for any DZ user is to run its set up test, which measures your hearing performance.

To do this there is the inevitable tablet or smartphone app that requires the headset to be connected via Bluetooth. The instructions are straightforward and worked first time, for me. This app is something akin to a hearing test done by an audiologist. It plays various tones and you adjust a volume slider so that you can just hear them (image 3). From that it calculates for each frequency, the amplification necessary to bring hearing sensitivity back to as near normal as it can (image 4). It then applies these settings to DZ and automatically sets them each time it is powered up.

On to flying. DZ has a controller in its audio leads (pic 5). A push button switches it on and off and lights flash when it is on. If it has a problem or its battery goes flat it defaults to a passive function (ANR off). It also has volume controls and a ‘multi-function’ switch that controls CO warnings (one press), HearingEQuity on/off (two presses) and other functions (press and hold) as well as buttons to control the secondary Bluetooth input (music, phone, tablet etc). While it defaults to HearingEQuity ‘on’ after switch on, if you have switched it on or off in flight or inadvertently knocked the button, there is no indication of where you are in its cycle. It would be convenient to have a light.

I was also a little concerned that the battery box (25% heavier than its predecessor) was weighing heavily on my headset sockets. Most headsets with such a box in the lead include a clip to take the weight off the plugs and sockets. There was none with the set I had and, while I used one from my own Zulu headset, it didn’t really fit the improved Kevlar-core leads used on DZ. Other than these points, it was comfortable and effective.

In-flight experience was great. I would normally have difficulty with some voices without my hearing aids, but with DZ the background noise was low and voices were clear. Female voices are a bigger challenge for many of us, as their higher pitch is a challenge for aging hearing

02 Typical reduction of hearing sensitivity with age. Being in the hearing loss zone doesn’t mean you can’t hear, but could present problems hearing accurately in noisy environments.

03 When you have done all 12 settings the app shows you the equaliser amplification profile it will use to correct your hearing. For me that was the maximum (+12dB I believe) above 4 kHz.

04 The Lightspeed app connects to DZ and plays tones. You adjust the slider (blue line) until you can just hear the tone.

05 Lightspeed Delta Zulu controller has two battery pack options. A lithium battery that’s USC chargeable and expected to last about 30hr. It provides a five-hr warning of charge required. A conventional AA battery cartridge is also included.

Human ears and aviation

Unwanted external noise is a big problem in some of our aircraft. When it is too loud it affects successful interpretation of radio or intercom messages, comfort and the health of our hearing. To counter this, various noise reduction aviation headsets have appeared.

Passive Noise Reduction (PNR) headsets achieve noise reduction by adding big padded earmuffs and gripping the ears (clamping) firmly to exclude external sounds.

More recently Active Noise Reduction (ANR) has been introduced in which the headset electronically detects, processes and produces an ‘opposite’ sound. When applied inside the earpiece this cancels the unwanted noise. This technique has become most effective and has enabled ear clamping or gripping forces to be reduced, substantially increasing comfort. Some of these devices are now so good that they not only eliminate the noise you don’t want but are beginning to affect sounds that you (as the pilot) need to be aware of, such as engine noise, stall warner or other audio alarms. For the top range of headsets, ANR technology is now very close to the safe limits of noise reduction. External noise has been dealt with as far as is safe, are there any other ‘aural limitations’ that could be addressed?

At birth the human ear generally responds equally to the full range of audible sound. High notes (whistles and beeps) sound as loud as low notes (rumbles and roars), so letters and words, made up of many such individual sounds, are clear. As most of us get older (into our thirties) our hearing response to high notes begins to deteriorate naturally. This phenomenon gets more pronounced in our mature years. As this happens slowly, our brains get used to the changes and most people don’t notice. Eventually, however, low frequency tones tend to dominate or swamp higher frequency tones even in a quiet environment and we may become aware of hearing difficulties.

Letters and words are made up of a series of tones of mixed frequencies, some high, some low, which if we are to interpret them accurately need to be heard as spoken. Words become unclear or muffled when the ear doesn’t detect all the component tones as intended.

All adults suffer from hearing response deterioration and after it gets beyond a certain point (typically 20-30dB loss), hearing clarity starts to deteriorate. Some words can become unclear or muffled. For example, S’s and T’s (low volume higher frequency letters) sound like Th’s or even vanish.

It becomes difficult to hear in noisy bars and restaurants, plus noisy equipment like vacuum cleaners and aeroplanes reduce hearing clarity. This can result in you mishearing some words in a conversation. For a while (in particular in a quiet environment) the brain intervenes, ‘guessing or predicting’ missed or poorly detected sounds leaving the listener oblivious to the presence of a problem. It’s only when the brain misguesses its interpretation of a sound or word do we misinterpret words or get lost in a conversation.

The noisier the environment, or the older we are, the worse this phenomenon becomes. This, like it or not, is a sign of age-related hearing loss and most of us suffer from it. Fixing it is not just a case of turning the volume up, it is more complicated than that but it can be done.

– me included, so my test focused on their higher voices. No problems. Being more objective I measured the ANR (image 6) and compared it to other top of the range sets I have tested before (image 7). Compare the two pictures. For DZ you will notice a bigger gap (more reduction) at lower frequencies (left side of graphs) between the outside noise (red) and the in-earpiece noise (green).

HearingEQuity

20KHz audio bandwidth is the ‘magic number’ bandied around by hi-fi enthusiasts that we must all be ‘able to hear’, and indeed DZ claims that bandwidth. But, 6 Khz is the maximum audio range for DZ’s (and most aviation headset) microphones and the Air Radio audio bandwidth is only 4 kHz. There are no more higher tones there to hear. While many of us would fall into hearing aid territory if we were trying to hear 20kHz music notes properly, for aircraft comms we are not, and even those of us with hearing loss at 8 kHz (the audiology normal limit) don’t need major technology to dramatically improve 4KHz air-radio clarity. To measure EQ’s effect, I conducted a simple comparison between DZ (with and without HearingEQuity) and my Zulu (with and without hearing aids). ANR was off. Image 8 illustrates the result for my ears.

In terms of clarity, DZ with HearingEQuity was nearly as good as my old Zulu with hearing aids, plus, when on, its ANR makes it quieter.