Certain Techniques With Regard To Decreasing The Noise In Wireless Speaker Systems

By Linda Cullmann


Are you searching to buy a new a set of wireless loudspeakers for your home? You may be dazzled by the amount of options you have. To make an informed choice, it is best to familiarize yourself with popular specs. One of these specifications is referred to as "signal-to-noise ratio" and is not frequently understood. I will help clarify the meaning of this expression.

Whilst looking for a pair of wireless loudspeakers, you first are going to check the price, power amongst additional basic criteria. Nonetheless, after this initial selection, you are going to still have quite a few models to choose from. Now you are going to concentrate more on a few of the technical specs, like signal-to-noise ratio as well as harmonic distortion. Every cordless speaker will make a certain level of hiss and hum. The signal-to-noise ratio is going to help compute the amount of noise created by the loudspeaker.

Comparing the noise level of several sets of wireless speakers may be accomplished fairly easily. Simply collect a few types that you want to evaluate and short circuit the transmitter audio inputs. Next set the cordless loudspeaker volume to maximum and verify the amount of noise by listening to the speaker. You are going to hear some amount of hissing and/or hum coming from the loudspeaker. This hiss is generated by the wireless speaker itself. Then compare several sets of wireless speakers according to the following rule: the smaller the level of noise, the better the noise performance of the wireless loudspeaker. On the other hand, keep in mind that you have to set all sets of wireless loudspeakers to amplify by the same amount in order to compare different models.

To help you evaluate the noise performance, cordless speaker producers publish the signal-to-noise ratio in their wireless speaker spec sheets. Simply put, the larger the signal-to-noise ratio, the lower the level of noise the cordless loudspeaker generates. One of the reasons why wireless speakers produce noise is the fact that they use elements such as transistors as well as resistors which by nature create noise. The overall noise is dependent on how much hiss every element produces. Nonetheless, the position of these components is also essential. Elements which are part of the loudspeaker built-in amp input stage will usually contribute most of the noise.

Noise is also created by the wireless broadcast. Different styles of transmitters are available that work at different frequencies. The least expensive sort of transmitters uses FM transmission and commonly broadcasts at 900 MHz. The level of hiss is also dependent upon the amount of cordless interference from other transmitters. Newer types will normally employ digital audio broadcast at 2.4 GHz or 5.8 GHz. This style of music transmission offers better signal-to-noise ratio than analog type transmitters. The level of hiss depends on the resolution of the analog-to-digital converters and the quality of other parts.

Most recent cordless speakers have built-in power amplifiers that include a wattage switching stage which switches at a frequency around 500 kHz. In consequence, the output signal of wireless loudspeaker switching amps exhibit a fairly big amount of switching noise. This noise component, however, is typically inaudible as it is well above 20 kHz. Yet, it can still contribute to loudspeaker distortion. Signal-to-noise ratio is usually only shown within the range of 20 Hz to 20 kHz. For that reason, a lowpass filter is used while measuring cordless loudspeaker amplifiers in order to eliminate the switching noise.

Makers measure the signal-to-noise ratio by setting the built-in amplifier such that the full output swing may be achieved and by feeding a test tone to the transmitter which is usually 60 dB below the full scale of the speaker amp. Subsequently, the noise floor between 20 Hz and 20 kHz is measured and the ratio to the full-scale signal computed. The noise signal at different frequencies is removed through a bandpass filter during this measurement.

Time and again the signal-to-noise ratio is expressed in a more subjective method as "dbA" or "A weighted". This technique was designed with the knowledge that human hearing perceives noise at different frequencies differently. Human hearing is most sensitive to signals around 1 kHz. Then again, signals under 50 Hz and above 13 kHz are hardly noticed. Consequently an A-weighting filter is going to amplify the noise floor for frequencies which are easily perceived and suppress the noise floor at frequencies that are hardly perceived. Most cordless speaker are going to show a larger A-weighted signal-to-noise ratio than the un-weighted ratio.




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