TRUSOUND SOFTENER

The TruSound Softener has been developed specifically to minimise the irritation caused by impulse sounds, or transient sounds as they are often called.

A recent study by Keidser et al. (2009) showed that transient sounds, such as a slamming door or rattling cutlery, tend to be perceived as much more annoying by hearing aid users than by normal-hearing listeners.

The purpose of the TruSound Softener algorithm is to make transient sounds less annoying without removing them or making them unnaturally soft.

Transient sounds come at all sound levels from soft sounds like computer key strokes or a ticking clock, to medium-level sounds such as clanging dishes or clattering cutlery, and loud sounds such as fireworks or hammer blows.

They are characterised by being very short (< 1 second) and rising to their peak value extremely quickly.

Loud transients will often exceed the hearing aid user’s uncomfortable loudness level if gain is not reduced. The problem with soft and medium-level transients is slightly different. When they occur in a frequency region where a fair amount of gain is applied to compensate for a relatively high degree of hearing loss, transient sounds will often end up sounding unnaturally distinct as a result. 

Certain speech sounds are also transient. For example, the English plosives /p, b, t, d, k, g/ have a transient part. It has been a very important goal during the development of the TruSound Softener that transient speech sound must never be attenuated by the algorithm.

Thanks to the Speech and Noise Envelope Characteristics Model in the Steep Gradient Detector, which is the detection mechanism in the TruSound Softener, transient noise sounds can be identified and handled efficiently and securely without speech sounds being affected in any way.

Because transient sounds are so brief, the system has very little time to react before it is too late. What is needed, therefore, is a compression system that is capable of instantaneous gain reduction. This is what we have achieved with the invention of the TruSound Softener.

With the introduction of the TruSound Softener in Widex CLEAR440 and SUPER440, instantaneous gain reduction becomes possible because transients are detected already in the broadband signal. This gives the system time to warn the compression system that it has to switch to a new, extremely fast-acting compression mode which can reduce gain instantly.

Widex’ overall fitting strategy is that soft sounds should be audible, speech should be intelligible, and loud sounds should be loud but not uncomfortable.

Our efforts to provide a comfortable listening experience must therefore never result in the hearing aid users being deprived of transient sounds.

Gain is therefore reduced relative to the user’s individual hearing loss to provide the users with a comfortable, yet realistic rendition of the sound environment they find themselves in.