In a previous installment of UE University we talked about the fantastic Sound Guard that UE debuted at NAMM this year. We spoke with Engineer Joe Saggio on some of the more technical sides of Sound Guard.
Hey Joe, thanks for taking some time to chat with us. Can you tell us about what Ultimate Ears Sound Guard does?
Sound Guard provides 2 functions. (1) Audio Signal Buffering (2) Audio Spike attenuation.
What do those things mean?
Audio Signal Buffering: Ensures that devices like multi-driver, low impedance IEMS do not interact poorly with the music player headphone output electronics and “distort” the originally designed audio frequency response. Provides an EASY TO DRIVE interface to the IEM for the music player.
Audio Spike Attenuation: Ensure that loud, transient or unintended sounds such as microphone pops (hot plug or unplug) & drops and/or feedback events are lowered in SPL so, although the user will hear it, it will be greatly reduced in level. In essence, problematic and potentially painful sound spikes and transients are reduced to more comfortable and safe levels.
Wow that’s pretty great! Is that like impedance matching?
Impedance matching is really an incorrect term in this case. Sound Guard is actually an Impedance Transformer. In that way, Sound Guard provides a very *low* source impedance such that it creates a *mismatch* with an in-ear monitor. Portable Solid-State devices such as iPods or wireless monitoring beltpack systems seek to deliver voltage to a load and typically can have trouble sourcing relatively large currents into low impedance loads. If impedances are MATCHED, then that voltage is split between the source output impedance and the IEM impedance thus creating a loss of signal and ultimately sound to the listener. By presenting a low source impedance to an in-ear monitor, the headphone retains a far greater magnitude of the intended audio voltage; The low source impedance provided by Sound Guard minimizes interaction between the SOURCE and IEM and thus renders the designed and approved IEM frequency response.How does Sound Guard protect the user’s hearing?
Sound Guard has an internal threshold, or, “setpoint”, above which the source audio signal is electrically reduced in gain. The internal circuitry does not “clip” the signal above the preset threshold, rather it reduces the amplitude while maintaining the signal’s original referential envelope in amplitude & time; the reduced signal is derived precisely from the original signal yet scaled to a lower level; this ultimately drives the attached in-ear monitor headphones set to a lower SPL than would have been originally experienced.
Additionally, each channel of the Left and Right stereo signal path has its own independent limiter so that spikes on either channel can be independently processed. Finally, the threshold and limiting are all accomplished with analog circuitry. There is no A/D conversion and no sampling delay time.
Why do my Ultimate Ears sound better when I am using Sound Guard?
Aside from the limiting function within Sound Guard, there is also a buffer that isolates the source device impedance from the in ear monitor impedance; the buffer is followed by an output drive stage that can source relatively large currents into heavy (low impedance) loads.
That is really fantastic info I feel like I have a better understanding of the way UE Sound Guard works! Thanks Joe!!
If you want to learn more about Sound Guard or have questions contact your UE rep or drop us a line here at UE University.
