The two types of custom adapters Aviation Headset take a different approach to reduce and optimize the sound a pilot hears in his or her ears.
Traditional Active Noise Reduction (ANR) headsets employ two miniature microphones—one measures the noise level outside the headset’s ear cup (the surrounding noise), and the other measures the level at the ear’ (inside the ear cup). A loudspeaker inside the ear cup then creates a ‘phase-inverted noise wave’— a sound wave whose peaks and troughs are the exact opposite of those of the external noise wave. This ‘filling the gaps’ approach effectively cancels out low-frequency noise, reducing the noise level that the pilot hears under his/her ear cups by several decibels.
Due to its focus on low frequencies, ANR technology best counteracts non-fluctuating, resonating noise such as the background hum a pilot hears in the cockpit of a jet say. It does little to overcome fluctuating noise (i.e. sounds that span higher frequencies) and sharp ‘impulse’ noises. Therefore with traditional ANR headsets, the attenuation (reduction) of such dangerous higher frequency sounds is typically handled by the ear cups themselves, which usually offer either passive or active (level-dependent) attenuation.
In contrast, Dynamic ANR’s approach addresses all frequencies—both low and high. It compromises several technologies and features:
First is level-dependent hearing protection. This employs two external microphones—built into FreeCom’s ear jacks—which measure the surrounding sound pressure level before sending this entire signal to the headset’s electronics box. This then analyses whether or not the overall sound level is above 84dB. If louder than 84dB, its software algorithm attenuates this sound to below 84dB (i.e. reducing a sound of 90dB by 6dB for example), before playing back this sound to the user—exactly ‘as is’—via the internal loudspeaker inside the ear jack.
This level-dependent hearing protection is then partnered by four additional features:
- Acoustic shock protection
For the instantaneous reduction of annoying transient sounds and improved listening comfort.
- High-resolution 16-band fine-scale noise cancellation
For optimized listening comfort in loud but not dangerously noisy conditions.
- Adaptive equalizer (high pass filter)
For extra attenuation of low frequencies in loud noise.
- Volume control
This allows the user to adjust the headset’s ambient awareness to suit their listening preferences and is particularly useful for pilots looking to compensate for an existing hearing loss.
This combined technological approach has several benefits: it addresses all frequencies of noise, not just the low ones; it provides the pilot with excellent ambient awareness in quiet—meaning they don’t need to remove their headset to hear and talk normally; and it provides a completely accurate representation of the surrounding soundscape, whatever the noise level.
This kind of accuracy is particularly helpful when holding face-to-face conversations and when needing to identify the slightest changes in engine noise (a common requirement for helicopter pilots).