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what types of outdoor wireless1617 .pdf


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what types of outdoor wireless
Are you looking to get a brand new a pair of wireless speakers for your home? You may be
dazzled by the number of choices you have. In order to make an informed choice, it is best to
familiarize yourself with common specs. One of these specifications is named "signal-to-noise
ratio" and is not often understood. I will help explain the meaning of this term. As soon as you
have narrowed down your search by taking a look at several key criteria, like the amount of output
power, the size of the speakers plus the price, you are going to still have quite a few models to
choose from. Now it is time to look at a couple of the technical specs in more detail. An important
parameter of wireless speakers is the signal-to-noise ratio. To put it simply, the signal-to-noise
ratio describes how much hum or hiss the speakers will add to the audio signal. This ratio is
typically shown in decibel or "db" for short. You can do a simple assessment of the wireless
loudspeaker hiss by short circuiting the transmitter input, setting the speaker gain to maximum
and listening to the loudspeaker. Generally you are going to hear two components. The first is
hissing. In addition, you will frequently hear a hum at 50 or 60 Hz. Both of these are components
which are created by the wireless speaker itself. Make sure that the volume of each set of
cordless speakers is pair to the same level. Otherwise you will not be able to objectively compare
the level of noise between several models. The general rule is: the lower the amount of noise that
you hear the higher the noise performance. In order to help you evaluate the noise performance,
wireless loudspeaker suppliers publish the signal-to-noise ratio in their wireless speaker
specification sheets. Simply put, the higher the signal-to-noise ratio, the smaller the level of noise
the cordless loudspeaker produces. There are a number of reasons why cordless speakers will
add some form of noise or other unwanted signal. Transistors and resistors which are part of each
modern cordless speaker by nature generate noise. The overall noise is dependent on how much
noise each element generates. Yet, the location of those elements is also significant.
Components that are part of the speaker built-in amp input stage will usually contribute the
majority of the noise. A further cause of noise is the wireless audio transmission itself. Generally
models that make use of FM type transmission at 900 MHz will have a comparatively large
amount of static. FM transmitters are quite prone to wireless interference which is why newer
products usually utilize digital music transmission. This kind of audio transmission provides better
signal-to-noise ratio than analog type transmitters. The amount of hiss is dependent on the
resolution of the analog-to-digital converters and the quality of other parts. The majority of modern
cordless loudspeakers use power amplifiers which are digital, also called "class-d amps". Class-D
amplifiers make use of a switching stage that oscillates at a frequency in the range of 300 kHz to
1 MHz. This switching noise may result in a certain amount of speaker distortion yet is typically
not included in the signal-to-noise ratio which merely considers noise in the range of 20 Hz and
20 kHz. Manufacturers measure the signal-to-noise ratio by means of setting the built-in amp
such that the full output swing may be achieved and by inputting a test signal to the transmitter
that is usually 60 dB underneath the full scale of the loudspeaker amp. Subsequently the noisefloor energy is measured in the frequency range between 20 Hz and 20 kHz and compared with
the full scale signal energy.
Often the signal-to-noise ratio is expressed in a more subjective way as "dbA" or "A weighted".
This method was developed with the knowledge that human hearing perceives noise at different

frequencies differently. Human hearing is most responsive to signals around 1 kHz. Then again,
signals below 50 Hz and higher than 13 kHz are hardly noticed. An A-weighted signal-to-noise
ratio weighs the noise floor in accordance to the human hearing and is typically higher than the
unweighted signal-to-noise ratio.


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