KR-20260064009-A - Multi-way piezoelectric speaker system

KR20260064009AKR 20260064009 AKR20260064009 AKR 20260064009AKR-20260064009-A

Abstract

The present invention relates to a piezoelectric speaker with a multi-way system, and more specifically, to a piezoelectric speaker comprising a plurality of piezoelectric elements and a digital signal processing device, which separates an input audio signal by frequency band and distributes the signal to a piezoelectric element suitable for each frequency band, thereby providing a flat frequency response. According to the present invention, by utilizing the characteristic of a piezoelectric speaker in which the frequency response characteristics vary depending on the area, a collected sound source is filtered into multiple different frequency ranges, and the filtered sound sources are distributed to multiple piezoelectric speakers with different areas for output, thereby providing a multiway piezoelectric speaker system having flatter frequency characteristics.

Inventors

안채헌
김세진

Assignees

한국기술교육대학교 산학협력단

Dates

Publication Date: 20260507
Application Date: 20241031

Claims (12)

As a multi-way piezoelectric speaker system, A speaker unit comprising a plurality of piezoelectric speakers, each having a different area and physically separated to provide acoustic output in different frequency bands; and, A digital signal processing unit that filters and separates an audio signal input from a sound source into multiple frequency bands corresponding to the number of the plurality of piezoelectric speakers, and distributes each separated signal to a piezoelectric speaker suitable for the corresponding frequency band. Includes, This provides a flat frequency response across the entire audible frequency band, Multiway piezoelectric speaker system.
In claim 1, An amplifier that amplifies each signal separated through filtering in the digital signal processing unit above. A multiway piezoelectric speaker system characterized by further including
In claim 1, The above digital signal processing unit is, In the above audio signal, a low-pass filter that passes only the low-frequency region; and, In the above audio signal, a high-pass filter that passes only the high-frequency region A multiway piezoelectric speaker system characterized by having
In claim 3, The above digital signal processing unit is, In the above audio signal, a mid-range pass filter that passes a specific band other than the low-frequency region and the high-frequency region A multiway piezoelectric speaker system characterized by further comprising
In claim 4, The above mid-range pass filter is, Having one or more filters of different frequency bands A multiway piezoelectric speaker system featuring
In claim 1, In each of the above piezoelectric speakers, The larger the surface area of the piezoelectric speaker, the lower the frequency band signal is input. A multiway piezoelectric speaker system featuring
In claim 1, Each piezoelectric speaker of the above speaker unit is, Arranged to be electrically insulated from each other A multiway piezoelectric speaker system featuring
In claim 1, Each piezoelectric speaker of the above speaker unit is, Providing electrodes at the edges A multiway piezoelectric speaker system featuring
In claim 8, The electrodes of each of the above-mentioned piezoelectric speakers are, Arranged to be electrically insulated from each other A multiway piezoelectric speaker system featuring
In claim 8, The above speaker unit is, PCB supplying current to the electrodes of each of the above-mentioned piezoelectric speakers A multiway piezoelectric speaker system characterized by further including
In claim 10, The above PCB is, Each of the above piezoelectric speakers is arranged to be electrically insulated from one another. A multiway piezoelectric speaker system featuring
In claim 1, The above piezoelectric speaker is, Composed of PVDF (PolyVinyliDene Fluoride) material A multiway piezoelectric speaker system featuring

Description

Multi-way piezoelectric speaker system The present invention relates to a multiway piezoelectric speaker system, and more specifically, to a piezoelectric speaker comprising a plurality of piezoelectric elements and a digital signal processing device, which separates an input audio signal by frequency band and distributes the signal to a piezoelectric element suitable for each frequency band, thereby providing a flat frequency response. FIG. 1 is a diagram illustrating the movement of air particles based on the frequency of the output sound, FIG. 2a and FIG. 2b are diagrams comparing the structures of a dynamic speaker and a piezoelectric speaker, FIG. 3 is a diagram showing the impedance of the speaker, and FIG. 4 is a diagram illustrating the relationship between the deformation of the speaker diaphragm and sound pressure. A speaker is a device composed of a diaphragm and a driver that moves the diaphragm. When electrical energy with frequency components is input into the driver of a speaker, the driver causes the diaphragm to vibrate in accordance with the input frequency characteristics. As this movement of the diaphragm causes the air particles, which are the medium, to move, areas of high and low density of the air particles are created, as shown in Fig. 1. The magnitude of the pressure change caused by this density difference is called sound pressure. If the diaphragm of a speaker generates a large pressure change per unit time, as shown in the upper diagram of Fig. 1, it outputs a sound of a higher frequency, and if it generates a small pressure change per unit time, as shown in the lower diagram of Fig. 1, it outputs a sound of a lower frequency. The dynamic speaker, which is the most common type of speaker among these, is a device that uses a voice coil as a driver, utilizing the interaction of magnetic fields between a permanent magnet and a coil. Figure 2a is a diagram illustrating the structure of a dynamic speaker. When current flows through the driver coil, a force is generated according to Fleming's left-hand rule, causing the speaker's diaphragm to move and push out air, thereby generating sound pressure. Unlike dynamic speakers, piezoelectric speakers, which are a type of speaker, have a structure in which the driving part is integrated with a diaphragm. This is because piezoelectric speakers utilize the characteristic of piezoelectric elements, which deform when voltage is applied. Figure 2b is a diagram illustrating the structure of a piezoelectric speaker. When voltage is applied to a piezoelectric speaker, the piezoelectric elements contract and expand in polarized directions, pushing out air. Sound pressure is generated by the movement of air produced in this way. Dynamic speakers are subject to shape limitations due to drivers composed of components, such as coils and permanent magnets, that are difficult to manufacture in various forms. However, piezoelectric speakers, which integrate the diaphragm and driver, overcome these constraints and can be produced in diverse shapes. Furthermore, the absence of a separate driver offers the advantage of being lightweight. In particular, the use of PVDF (Polyvinylidene Fluoride) piezoelectric elements allows for flexibility and transparency due to the properties of the polymer material, resulting in greater stability and versatility compared to brittle ceramic piezoelectric elements. An ideal speaker should output sound pressure equal to the input electrical signal. However, unlike this, actual speakers do not produce sound levels that are uneven across frequency ranges relative to the input signal, and one of the causes is the inherent frequency response characteristics of the speaker. The frequency response characteristics of a speaker are influenced by the impedance characteristics shown in Fig. 3 and are significantly affected by the material, shape, or mass of the diaphragm, as well as the circuit configuration of the speaker. The natural frequency of the diaphragm corresponds to the mechanical impedance in the frequency response characteristics of the speaker mentioned above, and causes sound distortion in that frequency range. In this case, the natural frequency of the diaphragm follows Equation (1), where λ is a value corresponding to the ratio between the length a of the long part and the length b of the short part of the piezoelectric speaker. According to Equation (1), it can be seen that a diaphragm with the same Young's modulus E, density ρ, Poisson's ratio ν, and thickness h has a natural frequency inversely proportional to the length a of the long part. Therefore, a speaker with a large diaphragm area has a natural frequency in a relatively low frequency range. (1) To avoid distortion at the natural frequency, speakers must output sound in a frequency range higher than that. Therefore, speakers with wide diaphragms having low natural frequencies can output a wider range of low frequencies. Additionally, as shown in Fig. 4, as th