It is easy to be confused by the terminology that wireless speaker suppliers utilize to depict the performance of their models. I will explain the meaning of one often used parameter: "signal-to-noise ratio" to help you make an informed choice when purchasing a new a set of cordless speakers.
As soon as you have narrowed down your search by glancing at a few key criteria, like the amount of output wattage, the size of the speakers and the cost, you are going to still have quite a few products to choose from. Now it is time to take a look at a couple of the technical specifications in more detail. An important criterion of cordless speakers is the signal-to-noise ratio. To put it simply, the signal-to-noise ratio describes how much hum or hiss the speakers are going to add to the audio signal. This ratio is customarily shown in decibel or "db" for short.
Evaluating the noise level of several sets of cordless speakers may be accomplished fairly simply. Simply collect a few types which you wish to evaluate and short circuit the transmitter audio inputs. Next put the wireless loudspeaker volume to maximum and check the level of static by listening to the loudspeaker. You will hear some amount of hissing and/or hum coming from the loudspeaker. This noise is created by the wireless speaker itself. Make sure that the volume of each couple of wireless loudspeakers is pair to the same level. Otherwise you will not be able to objectively evaluate the level of hiss between several models. The general rule is: the smaller the amount of noise which you hear the better the noise performance.
If you prefer a set of wireless loudspeakers with a small level of hissing, you can look at the signal-to-noise ratio figure of the data sheet. Most producers are going to show this figure. wireless speakers with a high signal-to-noise ratio are going to output a low amount of static. There are numerous reasons why wireless speakers are going to add some form of noise or other unwanted signal. Transistors and resistors that are part of every modern wireless speaker by nature generate noise. Generally the elements that are situated at the input stage of the built-in power amplifier will contribute most to the overall noise. Thus makers usually are going to select low-noise components whilst designing the cordless speaker amp input stage.
Static is also brought on by the wireless transmission. Different kinds of transmitters are available which work at different frequencies. The cheapest sort of transmitters employs FM transmission and usually transmits at 900 MHz. FM transmitters are extremely prone to wireless interference which is why newer products typically use digital music broadcast. The signal-to-noise ratio of digital transmitters depends mostly on the type of analog-to-digital converters and other parts which are utilized along with the resolution of the wireless protocol.
The majority of modern wireless speakers have built-in power amplifiers that incorporate a power switching stage that switches at a frequency of around 500 kHz. This switching frequency is also noise that is part of the amplified signal. Yet, today's wireless loudspeaker specifications normally only consider the hiss between 20 Hz and 20 kHz.
The most common method for measuring the signal-to-noise ratio is to pair the wireless speaker to a gain which permits the maximum output swing. Subsequently a test tone is fed into the transmitter. The frequency of this signal is generally 1 kHz. The amplitude of this tone is 60 dB below the full scale signal. After that, only the noise between 20 Hz and 20 kHz is considered. The noise at different frequencies is eliminated through a filter. Next the level of the noise energy in relation to the full-scale output wattage is computed and expressed in db.
An additional convention in order to express the signal-to-noise ratio utilizes more subjective terms. These terms are "dBA" or "A weighted". You will spot these terms in most cordless loudspeaker spec sheets. This method tries to examine in how far the wireless speaker noise is perceived by human hearing which is most sensitive to signals at frequencies at 1 kHz. An A-weighted signal-to-noise ratio weighs the noise floor according to the human hearing and is usually larger than the unweighted signal-to-noise ratio.
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