SE449411B - SET FOR SEATING SOUND EFFECT AT LOW FREQUENCY GENERATORS - Google Patents

Description

15 20 25 30 ___ _ .__..._ 449 411 In the event that the sound is generated by means of high-pressure air pulses, which are fed by a supply unit into a quarter-wave resonator, the sound effect is determined by the air flow, but also by the method with which the air pulses are fed in and how the sound generator is connected to the boiler. It is of great interest to know how much sound effect the sound exciter produces »to assess whether the sound generator is installed in a suitable way and whether the setting is optimal. To get an estimate of the power generator's power development, the sound pressure inside the boiler can be measured. However, it is often difficult or impossible to measure the sound pressure in the boiler due to the high temperature of the flue gases. In addition, the flue gas pressure is often higher than the ambient pressure. Even in cases where the sound pressure can be measured, it is difficult to get a measurement by conversion. power generation of the sound generator.

The present invention is based on a solution of these and others. related problems, and the method according to the invention is characterized in that the pressure amplitude at the closed part of a resonator tube of a sound generator is measured, whereby a signal is obtained, constituting a measure of the output power of the sound generator.

This utilizes the insight that there is a certain connection between the generated sound effect and the sound pressure at the closed end of a sound generator's resonant tube.

At the closed end of a quartz wave resonator, the following equation applies to the closed pressure part (Pa) = the density of the gas in the opening of the sound generator (kg / m) of the speed of sound of the gas in the sound generator. aperture (m / s) wavelength (m4) resonant tube radius (m) generated sound power (W) Pwmwroššo nu ll If the sound generator is operated with compressed air at a temperature of 20 ° C, the product Yo e will be 410 kg / (mzs) .The value will change slightly with the temperature, but since the temperature variations of the compressed air are usually relatively small, and moreover the sound pressure depends on the square root of the value, lcan this number with a sufficient degree of accuracy is assumed to be constant. \) 1 10 15 20 25 449 41.1 depends entirely on the constructive design of the sound generator. ~ k can also be specified as the number of waves per meter = 2%: where Å is the wavelength (m).

For a given given design on the sound generator, 4 P = K§ 0 applies, where the constant K mainly only depends on the dimensions of the sound generator.

The invention is further exemplified in the accompanying figure. In this, at 1 a resonant tube to a sound generator, for example a quartz wave resonator, is shown.

Compressed air (at 7) is fed to a feed unit 5, where sound is generated by means of high-pressure air pulses, which are fed by the feed unit 5 into the quartz wave resonator 1. The opening of the resonator 1 is connected to a space to be sooted, for example a boiler. 2. A certain minimum back pressure is thus required here.

The sound effect P is determined by the air flow, but also by the way in which the pulses are fed in, and of course also the connection method.

The pressure (po) at the closed end of the resonator is measured with the pressure sensor 4, and its output signal, which is an output AC voltage, is applied to a measuring instrument 6 via a filter and a rectifier 5, which converts it into a DC voltage signal which is proportional. against the amplitude po, and the sound effect can be read directly on the instrument 6.

Of course, the alternating voltage can also be read directly and possibly converted to sound effect P.

The output signal can be analog and / or digital, and it can possibly be used in a control device (not shown) for setting the desired sound power (P).

You can also manually, after obtaining the value P of the sound power signal, set the desired sound power.

The sound effect can be read directly on the instrument 6.

The method as above can be varied. manifold. within the scope of the following claims.

Claims (3)

1. 449 411 of PATENT REQUIREMENTS 1. Set the measurement and, if necessary, control of sound power in low-frequency sound generators, for example in sound-soothing generators, comprising a characteristic wave resonator with a closed part and an open part, such as resonant tubes, a sound resonator tube being connected to , characterized in that the pressure amplitude (fi o) at the closed part of the sound generator of the sound generator is measured, whereby a signal is obtained, constituting a measure of the output power (P) of the sound generator. 2. A method according to claim 1, characterized in that the ut-è power (P) is calculated according to the formula § '= \ / §fi._1 _ \ / ï ° 0 fr kaz where' fi o = am fi lititude of the sound pressure in a quartz wave resonator closed part (Pa) Y '= the density of the gas in the aperture of the sound generator (kg / m) c = the velocity of the gas in the aperture of the sound generator (m / s) k = the number of waves (m4) a = the radius of the resonant tube (m) P = the generated effect (w). 3. A method according to any one or more of the preceding claims, characterized in that the measuring signal (po) is applied to a conversion means, the output signal of which constitutes the output power (P), which signal can be analog or digital. 14. Set according to one or more of the preceding patent requirements, k 'a'. n n e - t e c k n a t of the fact that one of the above-mentioned measuring signals (po, 130, P) is applied to a control device for setting the desired output power (Pbör).