MXPA96003424A - Method to inspect an issuer of son - Google Patents

Abstract

The invention provides a method for inspecting a sound emitter comprising the steps of: producing a sound by applying a vibrational force of a certain basic frequency to the sound emitter and sampling the sound pressure level of the sound produced by a period of predetermined time, execute FFT on the sampled data to detect a maximum peak frequency, the number of peaks of the sound pressure level that are equal to or greater than a first threshold value, and the number of slopes of the sound pressure level that they are equal to or less than a second threshold value, assign to each detected value a membership degree according to a membership function defined for each of the evaluation items, weigh each degree of membership according to their contribution to obtain this a modified membership degree, and determine the acceptability of the sound issuer according to whether the sum of the degree of membr is modified is equal to or greater than a certain threshold value or

Description

METHOD FOR INSPECTING A SOUND EMITTER.

TECHNICAL FIELD. The present invention relates to a method for inspecting a sound emitter that emits sound activated by an applied vibrational force of a certain basic frequency.

ANTECEDENTS OF THE INTENTION. Conventionally * in the field of manufac. of sound-emitting devices, such as whistles, sonar or horns for vehicles, other than musical instruments, the method for evaluating the sound quality using measuring instruments has been substantially limited to simply measuring the pres- sure or frequencies of the sound. sound. As it is difficult to express the quality of sound quantitatively, the aunt sound has been evaluated, for example, by means of auditory tests conducted by inspection personnel. However, it was necessary for the personnel to be sufficiently expert to achieve a correct evaluation and the evaluation tends to be affected by the physical condition of the personnel. In accordance with the above, it has been desirable to find a way to express the quality of sound quantitatively. Devices such as those mentioned above are provided with one or a small number of oscillation modes and vibrate the air to emit sound. When a device of this type is of good quality, its pattern of spectra obtained by executing FFT on the sampled sound data will have a shape similar to a sag, since the peaks of the spectral data will appear in multiples or fractions I ( I represents integers) of a vibrational frequency (a basic frequency) of an applied force for emission of sound and frequencies that are not - multiple of the basic frequency are less frequent in their appearance. However, if a sound emitter is determined to be acceptable only when the peak peak frequency, the number of peaks and the number of slopes of the spectrum data are fully satisfactory with respect to the predetermined threshold values, those which can be accepted according to the complete evaluation of various properties of the sound. BRIEF SUMMARY OF THE INUNTION. To overcome the above-described problem, whereby the quantitative evaluation of the quality of the sound emitted from the sound emitter, which is activated by a vibratory force of a certain basic frequency, is permitted, the present invention provides a method for the inspection of a sound emitter, comprising the steps of: producing a sound by applying a vibrational force of a certain basic frequency to the sound emitter and -sampling the sound pressure level of the sound produced for a predetermined period of time ? executing an FFT on the sampled data to detect a maximum peak (maximum) frequency, the number of peaks (maximum) of the sound pressure level that are equal to or greater than a first threshold value, and the number of declines in the pressure level of sound that are equal to or less than a second threshold value i assign to each detected value a grade of score according to a defined membership function for each of the evaluation items: weigh each degree of membership in accordance with a contribution of the same to obtain in this way a modified membership grade; and determining the acceptability of the sound emitter according to whether the sum of the modified membership grades is equal to or greater than a certain threshold value or not. Therefore, even if a sound emitter has a property that is not entirely satisfactory, it can still be determined to be acceptable by the full evaluation in accordance with the present invention, using as the evaluation criteria, the maximum peak frequency, the numbers of peaks and declines in sound pressure level. Specifically, in the evaluation of properties, membership functions are used to determine the membership grades, when the output of each of the functions is one (1) when the property is inside, for example, of the "0K" region, zero (0) when the property is within the "NG" region and the value between zero and one when the property is between the two regions. The determined membership levels are weighted according to their contributions to the sound quality to obtain in this way the modified membership degrees whose sum can be compared with a certain threshold value to determine the acceptability of the sound emitter.

BRIEF DESCRIPTION OF THE DRAWINGS 2Q Now, the present invention is described in the following, with reference to the appended drawings, in which: Figure 1 is a diagrammatic configuration showing schematically the apparatus for inspection of a, 5 sound emitter? using the present invention. Figure 2 is a flow diagram showing the method for evaluating sound in accordance with the present invention. Figure 3 is a diagram showing an example Q of the spectral data of a horn; Figure 4 * is a diagram showing a membership function for determining membership degree X for a maximum peak frequency; Figure 5 is a graph showing a membership function to determine the membership grade Y for a membership. M number of peaks; and Figure 6 is a graph showing a membership function to determine membership grade I for the number N of declines, DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS, Figure 1 shows the configuration of the apparatus for inspecting a sound emitter using the present invention. As shown in Figure 1, the apparatus comprises a microphone 2 for capturing the sound emitted by the sound emitter to be inspected, such as a vehicle horn 1. An FFT spectrum analyzer 4 having an A / C converter to which a signal is sent from the microphone 2 via a sound level meter 3, stores the signal in its memory and provides the sound data to a controller 5 by means of the which the sound quality is evaluated according to the method of the present invention. The result of the evaluation is shown on a display device 6. The horn l of the vehicle has a contact that is opened or closed by a reciprocal movement of a plunger of a solenoid. The action of opening and closing of the contact leads the solenoid to the excited or non-excited state, whereby, through the piston, the diaphragm vibrates for the emission of sound. The amount of displacement of the plunger can be changed by means, for example, of an adjusting screw to change the period of the "open-close" movement cycle of the contact, so that the vibration frequency of the diaphragm is adjusted. The preferable vibration frequency is predetermined as a basic frequency in the design of the device. If the device is of good quality, the device resonates to the vibration at the basic frequency and emits the sound according to the design (sufficient sound pressure level and favorable tone). In accordance with the above, the quality of the device was conventionally evaluated by inspection personnel who perceived and verified the frequency or pressure of the sound when the adjusting screw is turned. With reference to the flow diagram of Figure 2, the method of the present invention for evaluating sound will now be described. In step ST1, the horn 1 is activated by a certain voltage, for example, provided by the controller 5, In the step ST2, the sound captured by the microphone 2, is sampled on the scale of the operating frequency of the horn , and then converted to A / C and stored in analyzer 4 of FfT spectra. In step ST3, the voltage applied to the horn t ceases to be applied, and in step ST4, FFT is executed with respect to the sound data stored in the memory to obtain the spectral data of the sound. In step ST5, as shown in figure 3 as an example, the peak frequency frequency fmax or a frequency providing the maximum peak are detected from the spectrum data; the number of peaks (P1 ** »P6) of the level of sound pressure that are equal to or greater than the first threshold value TI; and the number of declines (Vt ^ d) of the sound pressure level that are equal to or greater than a second threshold value T2. In the example of figure 3, the number M of peaks is six, and the number N of slopes is five. In the following stages ST6 ~ ST8, each of the detected values is assigned a membership grade in the "NG" set according to a corresponding membership function that is defined according to a certain design consideration for each evaluation item. In step ST6, as shown in figure 4, the degree of membership X is determined for the maximum peak frequency fmax. When fmax is within a predetermined scale associated with fully satisfactory frequencies, the degree of membership is set at zero, and when fmax is within a scale associated with totally unsatisfactory frequencies, the degree of membership is set at one. In addition, when fmax is between two scales, the degree of membership is fixed to a value that increases proportionally from the extreme of the scale associated with satisfactory frequencies until the extreme of the scale associated with totally unsatisfactory frequencies according to the function of membership (a solid line in figure 4). It will be emphasized that in the event that the scale associated with satisfactory frequencies is assigned a membership of degree one, the membership function will be that one shown in interrupted lines in Figure 4, In step ST7, as shown in FIG. figure , the degree Y of membership for a number M of peaks, is set to zero when M is equal to or greater than the lowest number totally satisfactory. When M is less than the lowest number, the degree Y of membership is set at a value that increases proportionally from the lowest number totally satisfactory to the highest number within a scale associated with totally unsatisfactory numbers in accordance with the membership function shown by a solid line in figure 5, again, in the case of the scale associated with totally satisfactory numbers is assigned a membership degree of one, the membership function will then be the one shown with interrupted line in Figure 5, In step ST8, as shown in the figure 6, membership grade I for the number of gradings, is terminated according to a membership function similar to that used to determine the degree of membership of the number of members. Again, in case the scale associated with fully satisfactory numbers has a membership grade of one assigned, the membership function will be like that shown by a broken line in Figure 6. It will be emphasized that in determining the membership level of the number of declines, the degree of membership is set to zero when the number is equal to or less than the number of plus an was within the scale associated with totally satisfactory numbers, and is set to one when the number is equal to or greater than the number number of the scale below associated with totally unsatisfactory numbers, because in the event that high peaks are difficult to form, many low peaks tend to appear, resulting in many declines. Therefore, each of the membership degrees X, Y, Z is determined using the correspondingly specified membership function. In the example, the degrees of membership in "N6" are determined, therefore the sound emitter is of better quality when the degrees of membership approach zero. However, the membership degrees in the "0K" sets can be determined where the sound emitter is evaluated to be of better quality, when the membership degrees are closer to one. In step ST9, each of the membership counts determined in steps ST6 ST8 is weighted in accordance with its contribution to sound evaluation. Membership grades are multiplied by coefficients A, B, C, respectively, and heavy membership degrees are aggregated together to have the sum L, that is, (AX + BY + Cl), which is used as a critical value for the evaluate uacidn. In step ST10, the critical value L is - -compared with a predetermined threshold value K. In the example, if the critical value L is equal to or less than the threshold value K, the process proceeds to step ST11, if the critical value L exceeds K, the process proceeds to step ST3; 2 and UNG "is indicated It has been confirmed experimentally that if the sound emitter is in resonance with a vibrational force of a basic frequency to emit sound efficiently, peaks of sound pressure appear in multiples (or fractions I, where I represents integers) of the basic frequency and are less likely to appear at frequencies that are not multiples of the base frequency, resulting in a spectral pattern that has a camber-like shape, and the maximum peak frequency appears on a narrow frequency scale. which comprises a multiple of the basic frequency, it is therefore possible to evaluate the sound quality in accordance with whether the maximum peak frequency is within a certain scale comprising the multiple s of the basic frequency and if the spectral pattern has a specific shape similar to a camber. These properties are expressed in a quantitative and heavy manner in accordance with their contribution to the evaluation, which allows the determination of the acceptability of the sound emitter. It is emphasized that although the sound emitter has been shown as an electric vehicle horn, this invention is not limited to a vehicle horn and can be any device that emits sound activated by a vibrational force of a basic frequency and the present invention can be applied to, for example, whistles or sonar. Therefore, in accordance with the present invention, the acceptability of a sound emitter of the type that emits sound activated by a vibrational force of a basic frequency can be determined by spectral analysis of the sound emitted using the maximum peak frequency, the number of peaks, and the number of gradients, as criteria for the determination, based on the fact that the emitter of the sound of the type has a peak frequencies in multiples (or fractions I, where I represents integers) of the basic frequency and The spectral pattern has a cambering configuration when the sound is effectively emitted in resonance. Therefore, the inspection of a sound emitter can be automated without relying on the auditory test by virtue of the quantitative evaluation, which will be significantly advantageous over the prior art.

Claims (1)

1. SINGLE CLAIM, A method for - inspecting a sound emitter, comprising the steps of: Producing a sound by applying a vibrational force of a certain basic frequency to the sound emitter and sampling the sound pressure level of the sound produced for a predetermined period of time; perform an FFT on the sampled data to detect the maximum peak frequency, the number of peaks of the sound pressure level that are equal to or greater than a first threshold value, and the number of equal pressure level declines that are equal ao less than a second threshold value; assign to each detected value a degree of membership according to a membership function defined for each evaluation item; weigh each membership grade in accordance with a contribution from it to obtain a modified membership grade; and determining the acceptability of the sonic emitter according to whether the sum of the modified membership degree is equal to or greater than a certain threshold value or not. R E S U E N. The invention provides a method for inspecting a sound emitter comprising the steps of: producing a sound by applying a vibrational force of a certain basic frequency to the sound emitter and sampling the sound pressure level of the sound produced by a period of predetermined time; perform FFT on the sampled data to detect a maximum peak frequency, the number of peaks of the sound pressure level that are equal to or greater than a first threshold value, and the number of sound pressure level declines that are equal to or less than a second threshold value; assign to each detected value a membership grade according to a defined membership function for each of the evaluation items; weigh each degree of membership according to their contribution to obtain a modified membership grade; and determining the acceptability of the sound emitter according to whether the sum of the modified membership degree is equal to or greater than a certain threshold value or not.