Earproof PRO Filter Platinum 15db – set by Arthur Stone
Introducing…the Earproof PRO 15dB: When starting this series of Earproof reviews I thought it would be enough to describe the outer ear and how the device fits in and affects perception of external sound - but the Earproof PRO is affecting the internal auditory system up to the point of ‘analogue-to-digital conversion’ (air pressure to mechanoreceptor to nerve impulse) and beyond.
The affordable Rockitt and mid-price Concert 15 dB reviews covered the basics: the historic development of earplugs, from full-bandwidth beeswax to Earproof’s medical-grade thermoplastic (TPE) which leaves no residue or stickiness. The selected bandwidth and semi-open, breathable filter design solves the issues of overheating, claustrophobia, and sensory imbalance inherent in older full-bandwidth types.
Why do we need earplugs? Specifically: for listening to music? It’s perhaps more understandable for noisy work environments; but why for music? Wouldn’t it be easier to listen at a safe level?
People are enervated by loud sound. A musical performance at a safe listening level will not energize an audience as an unsafe level will. Given a free choice people often play music louder than is safe…it’s a generalization.
There is a limit to how unsafe the level can be (too loud/uncomfortable) before becoming the worse option (probably age- and culture-dependent); but still, unsafe is the preferred option: the physical energy of the over-powered music makes the experience more visceral.
So the ‘augmented, advanced earplug’ – the Earproof PRO - allows us to hear sound louder and for longer than would normally be safe: no hangover effects such as ear ringing or impaired hearing the next day; healthier voice from lack of need to shout.
That’s a punter’s perspective anyway, perhaps more applicable to the audience-focussed Earproof Rockit and Concert, whereas the PRO is addressing the non-punter – the critical listener, performer or audio worker.
Why wear the PRO’s?
1/ To protect the ears and auditory system from high SPL by semi-blocking the ear canal and creating a vacuum seal. Peak SPL and sustained sounds can cause permanent deafness (either general or at specific frequencies); also short-term damage that affects real-time performance. Damage can occur below the SPL threshold that the listener feels discomfort so they may be unaware damage is occurring or that hearing is compromised. The Earproof PRO is offering 15 dB of leeway or headroom.
2/ The PRO’s attenuation maintain the ear’s optimum operating window in high SPL environments. With Earproof PRO’s inserted, the ear’s natural defences from loud sound are not as active. The high SPL experience is closer to regular perception of a lower-level reference sound.
3/ The Earproof PRO reduces Acoustic Reflex – the unconscious mechanism by which the human body protects the ear by dampening auditory system amplitude via muscular contracture and internal neurotransmission.
4/ The Earproof ‘vacuum seal’ design counteracts the Occlusion Effect - the human body’s internally-generated sound (heard with fingers in ears whilst speaking).
5/ Reduction of Lombard Effect (instinctive tendency to raise vocal level as environmental noise increases). The Earproof PRO is designed for applications where the nuances of the original sound need to be heard but at lower level; nearer to a reference mix balance.
Vocalists and players can overcome the unconscious tendency to raise vocal level in, for example, a live tracking session, affecting not only the level of the vocal/instrument but also the character and timbre.
Any Cons? Not really. There may be circumstances and styles that rely on the acoustic reflex. The user needs to put in some time to adapt the new hearing environment e.g. as with new monitors. Not cheap if they don’t support your performance needs. Will need to be replaced at some point depending on wear and care.
Price: 50 Euros (per pair) from Earproof.com online shop. A -10 dB (‘silver’) and -25 dB (‘gold’) version also available for the same price.
Specs: The Earproof PRO is a well-designed and manufactured product. It feels high quality. Each set of Earproof PRO’s are supplied with two sets of sleeves of adjacent sizes; this allows some leeway for fitting.
Fitting the Earproof PRO is straightforward; it may take a couple of go’s to perfect the technique. Earproof have a demonstration video here.
I didn’t experience any problems using the Earproof products; always follow Earproof’s instructions and if you do experience any pain or discomfort have your ears checked by a professional, doctor or audiologist.
The independent lab data published by Earproof shows the relative attenuation across the frequency spectrum with the Rockit and Concert having a less flat response yet still suited for their intended roles. There is no published data for the PRO so I’ve drawn a chart based on my perception in comparison to the Rockit and Concert specs.
NB actual effective protection value is lower. Here we’re focussing on the perception of sound.
The Biological Analogue-to-Digital Converter: The cochlea is an internal structure in the inner ear across which sound frequencies are mapped – a tonotopic map. The basilar membrane (inside the cochlea) contains sensors that react to high frequency signals at one end of the membrane (place coding) and bass frequencies below 200 Hz (temporal coding) at the other end which is coiled like a seashell. The membrane has a gradient of flexibility with the coiled bass end being the most flexible; the membrane physically vibrates or resonates in sync with the incoming bass frequencies, reproducing the external sound, and this can actually be recorded with a microphone. Sound can literally tickle your ears.
All this activity is at the stage of conversion: the music as sound (differential in air pressure) enters the spiral waveguide of the outer ear, through the ear canal, vibrating the eardrum, ossicles and cilia hairs attached to mechanoreceptors and is converted to an electrical signal (an axon potential) as represented physically on the membrane.
Despite the relative anatomical size of the ear it plays a large role in our sensory perception of the world. Grabowski says: “The ear is an engineering marvel because its sensory receptors can transduce sound vibrations with amplitudes as small as the diameter of an atom of gold (0.3 nm) into electrical signals 1000 times faster than photoreceptors can respond to light.”
In addition, the bi-lateral positioning of the ears on the sides of the head puts us at the centre of a 360 degree sonic environment; complex sensory 4D (position and time) information for the ears to collect and brain to decode.
The Perceptual Noise Floor: Basically, there is a perceptual signal-to-noise ratio (the noise being internally-generated). This occluded inner sound affects the dynamic response of the system by raising the noise floor. I hesitate to call it ‘dither’ – which is added, whereas occluded body sound is an inherent part of the operating system. Nonetheless, we can still hear its absence or increase.
Meditators will recognise internally-generated sound as being a deep-rumbling (of the circulatory system) and a pink noise with high pitch (the nervous system). There is bone conduction from the skull and skeletal system too; movements, breathing, creaky bones, gastro-intestinal gurgling and the like, etc.
The muscles have two types of fibres: slow twitch and fast twitch. Slow fibres contract at (approx.) 10 to 30 times a second; fast fibres at 30 to 70 – equating to sound at those frequencies in Hz. This internal sound can be heard by tensing jaw or placing clenched fist to ear. Similarly, the acoustic reflex, which the Earproof PRO alleviates, can also add to the noise from the body.
In addition there is a lot of internally-generated ultrasound. This is created by neuronal activity – the firing of axons – the physical opening and closing of billions of physical gates that correspond to brain/mind activity, thought patterns and thinking. True, we don’t hear external ultrasound with the external ears as such, but it does increase the internal processing bandwidth of the auditory and related systems.
Wearing an audio engineer’s hat, it’s obvious that if a component early in the signal path is compromised (e.g. the mic membrane is mechanically/physically overloaded) then this will affect the performance of the following components in the signal chain; and, this problem cannot be fixed later.
Similarly, in the outer- and mid-ear, if the eardrum and ossicles (the mechanical, vibratory part of the ear) are overloaded then the signal to be electrically-transduced in the inner ear is compromised – and this compromised signal is to be amplified 20x by the ossicles in order to impedance-match from ‘air vibration’ to ‘fluid vibration’ in the cochlea. The components of the ear evolved in the deep oceans of time; we still listen to sound waves through the fluid-filled inner ocean.
Acoustic Reflex (an organic dual-stage limiter/compressor): This can be divided into the ‘attenuation reflex’ and ‘auditory reflex’ – attenuation being a response to loud environmental sound, and auditory referring to a pre-vocal anticipation of speech or song. Both reflexes are unconscious, automatic, and instinctual.
Two tiny muscles (in each ear) react to loud sound and act to limit stress on the auditory system: the ‘tensor tympani’ muscle – connected to the trigeminal/mandibular nerve – limits movement and increases tension on the eardrum; the ‘stapedius’ muscle is connected to the facial/cranial nerve and dampens the movement of the stapes. Both ears respond simultaneously if one is triggered; stereo-linked. Damage to the stapedius muscle is associated with abnormally-sensitive hearing.
This makes sense when we think of grimacing at loud noise; the grimacing enervates the tensor tympani and stapedius to dampen the system by tensing the eardrum and ossicles, in a sense limiting the dynamic range during loud sounds. The attenuation reflex only operates with more sustained sounds (e.g. thunder) whilst fast peaks (e.g. snare hit) under 40 milliseconds get through unaffected.
The acoustic reflex threshold (ART) is generally between 70-100 dB SPL (for a specific frequency) but can be lowered by playing a secondary tone at a lower frequency than the trigger; either ear can be a trigger for both sides. This shows that the human ear’s limiting/compression system is adaptive – and stereo-linked. There are even ‘mid-side’ functions.
The brain’s auditory centre can also send neurotransmitter signals (glutamate) to the cochlea; this shortens the length of the cilia, limiting the dynamic range of the ear’s mechanotransducer system in response to high SPL.
The compression detector circuits are feedback based (attenuation reflex) or feed-forward (auditory reflex). Unlike plug-ins, look-ahead capability is not available (unless one includes the listener’s anticipation of an event) so again the Earproof PRO’s not only offer protection against unexpected peaks and sustained loud sound but will also reduce facial stress, and noise-induced ugliness.
ART and performance: The Acoustic Reflex Threshold (ART) is determined by sound pressure level (SPL) and frequency and generally kicks in around 70-100 dB. This is interesting in relation to studio monitoring levels (which for arguments sake are also around 70-100 dB): I prefer to monitor quietly e.g. 75 dB and I wonder if this choice is just under my ART? Do I unconsciously prefer this monitoring level (for detailed, long-duration work) because the acoustic reflex isn’t triggered?
The bigger question then is: if I want to make music that will be heard in SPL environments over the audience’s ART (that triggers their acoustic reflex), then do I need to mix/monitor at that level (with my acoustic reflex triggered) too?
The same question might apply for performance too: is the acoustic reflex a necessary part of the performance e.g. Death Metal? Punk? Reggae?
The ART is around 20 dB under uncomfortable SPL but ear damage can occur below discomfort level (particularly with duration) so the listener may be unaware damage is occurring. In super-loud SPL environments, the -15 dB attenuation of the Earproof PRO’s will still protect the ears, even if the ART is surpassed, but for performance – to prevent the ART being reached and impairing the vocal – more attenuation would be necessary. Earproof also make a -25 dB version for louder environments.
This requirement separates the Rockitt and Concert (which only need to protect the ears) from the PRO which needs to protect against triggering of the acoustic reflex in order to be effective for performance.
In Use: The obvious question was how close to regular hearing would the Earproof PRO’s be? The -15 dB attenuation is remarkably accurate, as is the representation of the original frequencies especially when heard above normal listening volume.
The Earproof Concert’s had full low-mids and upper-bass (great for the concert/live gig vibe) whereas in situations where more accuracy is needed e.g. playing bass, then the PRO’s more accurate representation of the original source sound comes into play.
Test tracking: electric bass (through Amplitube into amp and small PA); synths – Moog Subphatty and Waldorf Streichfett; amplified electro-acoustic; electric guitars through amps; mixed percussion (djembe, bodhran, bongos); acoustic guitar solo with background tracks to simulate small solo gig in noisy pub room (and here I was looking more at the Earproof PRO as an aid to performance focus in a distracting environment).
I wondered if there were weak areas or if the PRO’s gelled well with tracking needs for a variety of instruments? Whereas the Earproof Rockit and Concert reviews were focussed more on the passive listening experience, this PRO review is more about active participation in the music one wishes to attenuate.
Cranking it up: In a loud session, everything sounded ‘better’. The useful signal-to- noise ratio was improved – the important aspects of the music stood out - the slight sense of isolation the PRO’s gave was a positive and I didn’t feel distracted by buzzing amps or background noise. The guitar signal was clear and compressed. The sound was more intelligible than without. With the increased level I could crank the amp and feel it with my body. I felt like I could do a long, loud session without fatigue.
With the hand drums I could really give them a loud smack without the transients hurting; there was a slight loss of some of the high-frequency ‘edge’ of drum strikes; like a transient filter. The sound was less sharp and more rounded. Again, if I were playing percussion for a long session the PRO’s would be preferable.
With my vocal, the Occlusion Effect of internally-generated sound was more obvious – almost like an inverse comfort-reverb. Although there was less tendency towards the Lombard Effect, the automatic auditory reflex with ossicle-damping still occurred (as this is an anticipatory gesture preceding vocalisation). In general, using the Earproof PRO’s for vocals may require some practice or acclimatisation. It is a different perspective on how we hear ourselves: I was reminded of the singer’s trick of placing a finger on the tragus (inner lobe) of one ear to help with self-monitoring by blocking sound from the rear of the head (which is slightly delayed by the tragus to assist with orientation) and increasing occlusion at the resonant pitch.
Overall I think the Earproof PRO is a valuable asset for loud environments; the isolation makes the experience more enjoyable and accurate.
Rolling in the Deep…where sound becomes experience: So the Earproof PRO sits at the sweet spot in the signal chain; by preventing overload it allows the downstream components to function within norms. The signal-to-noise ratio is improved when the listener is in an environment with a higher SPL than the auditory system has evolved to operate optimally in.
The potential benefits of the Earproof PRO extend into the depths of the brain’s neural network, in particular, the thalamus, where auditory information is processed alongside attention and awareness.
There are 6 (known) tonotopic maps, starting with the basilar membrane of the cochlea and these tone-maps mediate sensory signals from the inner ear to the primary audio cortex of the brain.
After progressing though each tonotopic region the signal is recombined into a single stream from which the original sonic elements are again decoded onto a new map, then finally merging with the central audio cortex and attention regions at the brains core. We experience whatever we are aware of and pay attention to.
The ability of the tonotopic map to fold in 3D creates a nexus of information; e.g. neurons that recognise particular frequencies or timings are positioned adjacent, or linked to, other related neurons. Complex sound information morphs into living, growing, neuronal architecture.
At this depth no two human auditory systems are the same; the tonotopic network is as unique as a fingerprint or earprint or snowflake or the different forms of the radiolaria (in the image above).
Conclusion: The most valuable gear you own is between your ears; millions of years in development with countless happy users. For all of us fortunate to have good hearing, it makes sense to protect it. The Earproof PRO’s protect hearing in loud environments and improve performance by working with the natural design of the ear rather than being some semi-external blocker of sound like traditional or inferior earplugs. By attenuating sounds early in the auditory signal chain the downstream components function in the natural sweet-spot.
In addition to protecting hearing and making perception of sound more manageable, the PRO is adding a performance advantage by taming the Acoustic Reflex.
We likened the Rockitt’s to sunglasses for the ears; and the Concerts to Polaroid sunglasses. The PRO’s are like reactive sunglasses in comparison; they protect but also keep the scene closer to natural vision. Bottom line; don’t stare at the Sun.
Sound Quality 5/5 Very good. Preferable to overloading ears. This is quite a mature technology and the design and materials assist in keeping a balanced sound image with attenuation but without side-effects like occlusion or an uneven frequency response. Stereo-field and spatial awareness is good.
Ease of Use 5/5 A bit fiddly to start but invisible in use; whereas the Concert and Rockitt lost a point for ease of use, it’s fair to expect some adjustment over time as with new monitors or instrument or gear. Comfortable. Reliable sonic reference. Less gurning.
Features 5/5 Good, simple design that works with both the ear and the sound. Quality materials and construction. Handy container.
Bang-for-Buck 4/5 The sonic differences between the Rockit, Concert, and PRO, are reflected in their prices with a slightly-diminished return between Concert and PRO (kinda like monitors). Your ears (and music) are worth it but I’m not aware of any added value between the Concert and PRO in terms of materials or design – just different frequency responses for different uses and environments. Maybe there are factors that justify the extra cost, but they are not evident.
Credits and links:
By Morten Bisgaard - From the book "Tidens naturlære" 1903 by Poul la Cour, Public Domain, https://commons.wikimedia.org/w/index.php?curid=1030099
By Dr Michel Royon (User:Royonx) - rotated file:4-Triton.jpg by Dr Michel Royon (User:Royonx). Rotated by User:Snek01., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=7147566
Product images used courtesy of Earproof; additional images by Arthur Stone.