JP6268353B2 - Distributed arrangement type piezoelectric speaker network system and piezoelectric speaker device - Google Patents

Description

  In the present invention, piezoelectric speakers composed of piezoelectric ceramic vibrators and lightweight honeycomb diaphragms are distributed in an area so that circles having a radius of sound arrival distance are in contact with each other so that clear sound can be transmitted throughout the area. The present invention relates to a distributed sound transmission network system and a piezoelectric speaker device for the purpose of disaster prevention warning and guidance.

  In recent years, in order to protect residents from disasters caused by earthquakes, tsunamis, fires, accidents at nuclear power plants, etc., it has become an urgent issue to install a disaster prevention alarm speaker system that provides alarm notifications in the event of a disaster. Various disaster prevention information network systems have been proposed so far, and large-sized dynamic speakers and special-type magnetic speakers are used for the speakers in order to reach a wide area in a wide area. Since the sound emitted from these large speakers is loud near the speakers, the ears cannot withstand. In addition, there are problems such that it is difficult to hear sound due to sound reflection from buildings and mountains, and when a plurality of speakers are installed, the sound of the speakers interferes and the contents of the broadcast cannot be determined. Many of the devices are large, heavy and have a power consumption of several hundred watts.

  On the other hand, a large number of small and medium dynamic speakers are distributed in the area, and when the audio signal current is sent from one base station together, the current value is large, so a voltage drop occurs in the wiring to compensate for the voltage. The amplifying device must be designed to handle high voltages and large currents, which is not practical.

  Furthermore, since dynamic speakers interfere with each other's sound, there is a problem that if a large number of speakers are arranged, the sound becomes difficult to hear due to the sound interference between the speakers.

  In addition, since dynamic speakers have directivity in the generated sound, it is necessary to devise the arrangement of the speakers in order to distribute the sound uniformly in the area.

  Speakers generally used in conventional disaster prevention information systems are mainly of the magnet type and have a structure in which a drive coil is arranged in the magnetic field of a permanent magnet, which converts electrical signals into piston reciprocating motion of the drive coil. The vibration plate is vibrated to generate sound. Because this drive coil and diaphragm and the metal parts that support it are heavy and have a large inertial force, it is difficult to follow a fast acoustic pulse signal. Since vibration continued for a long time with respect to the acoustic pulse signal, a complicated noise waveform was generated, the sound was crisp, and it was difficult to produce clear sound. For this reason, a normal large-scale disaster prevention speaker has to speak slowly and is difficult to hear.

Large-scale disaster prevention alarm speakers are heavy, such as 50 kg (300 W type) to 150 kg (1300 W type), and in recent years there have been accidents in which speakers attached to pillars and buildings fall from high places during an earthquake and damage people and equipment. It has occurred frequently during earthquakes, and its danger has been greatly pointed out.
In addition, in a centralized disaster prevention warning system, if one location breaks down due to a disaster, there is a risk that the system in the entire region will be disabled.

  Furthermore, since a conventional dynamic speaker has a large audio current of 5 A to 10 A flowing through one speaker, a large current of several tens of amperes is required to drive a large number of speakers in a distributed manner and drive with one amplifier. The amplifier is also huge, and production is not realistic in terms of cost and technology.

  A plurality of piezoelectric drivers are arranged on a honeycomb diaphragm in which bending force is applied to the diaphragm or bending stress remains in the diaphragm, and the arrangement is devised so that the frequency band of human voice is 600 Hz to 4 KHz. Bands can be generated efficiently.

Stress is applied to the diaphragm, and the piezoelectric speaker in which the piezoelectric elements are effectively arranged has a smaller sound attenuation than the dynamic speaker due to the transverse wave effect or the coherent effect. Compared to the 6 dB attenuation of the dynamic speaker when the distance is doubled. Piezoelectric speakers are as small as 3 dB, which increases the sound reach.
Further, this voice waveform has no directivity and has a feature that it spreads radially at 360 degrees as well as before and after.

  In addition, because the diaphragm and piezoelectric driver are lightweight in piezoelectric speakers, the diaphragm can easily follow the sound signal, and the diaphragm can also be easily attenuated. To emit.

  Reverberation is extremely low compared to dynamic speakers due to the shear wave effect or coherent effect.

  The present invention makes use of the characteristic that the sound reaches radially far and uniformly, and a plurality of piezoelectric speakers are distributed in the area so that the circles having the radius of the sound arrival distance touch each other. Thus, it is possible to reach a voice that is clear and has little variation. For this reason, it is a system suitable for regional disaster prevention warnings with the objective of clearly reaching out the voices of people such as warnings and guidance, and the occurrence of landslides in areas near coasts or rivers where there is a possibility of tsunami damage. It provides a disaster prevention warning network system that can be used in easy-to-use areas and areas near nuclear power plants.

  In addition, the speaker network system is light and small with a weight of 1 kg or less, and is less likely to damage people and equipment when the speaker falls due to an earthquake or the like.

  The present invention not only transmits disaster prevention alarms, but also commercial areas such as shopping malls, premises and large traffic facilities, large amusement parks, sports facilities such as gymnasiums and stadiums, campuses such as universities, factory sites, airports, and harbors It can also be applied to systems that widely transmit clear audio.

  In addition, it can be applied to school traffic roads, traffic accident-prone areas, schools, residential areas, and other areas to transmit traffic safety information and emergency crime information.

  Piezoelectric speakers can be attached not only to dedicated broadcasting equipment in the area, but also to vending machines installed in large numbers in the area, as well as in convenience store buildings.

  When power cannot be supplied, an independent power source combining solar power generation and a storage battery system can be used. Piezoelectric speakers have a current consumption as low as 1/20 to 1/100 compared to dynamic speakers, and can be operated for a long time with a storage battery.

FIG. 1 is a diagram for explaining a piezoelectric speaker network system in a regional area.
Distribute and arrange piezoelectric speakers in the area so that the circles with the radius of the sound arrival distance touch each other, send audio signals wirelessly or by wire from the base station, and transmit clear and less-variable audio throughout the area I can do it.

  FIG. 2 is a circuit diagram for distributing audio signal current from a piezoelectric amplifier to a piezoelectric speaker wired to a speaker distributed in an area. Since the piezoelectric speaker has a high impedance, the current consumption is very small. Even when the piezoelectric speaker is connected in parallel, the voltage drop is small, and even if the piezoelectric speaker is connected by a thin wire, the sound pressure of each piezoelectric speaker is small and constant. In addition, power consumption is extremely small, 1/20 to 1/100 or less, compared to dynamic speakers. Therefore, 5 to 10 piezoelectric speakers can be driven by one piezoelectric amplifier.

  As a result of distributing 4 piezoelectric speakers with an acoustic distance of 250m in an area of 1km2 and delivering sound with a sound pressure of 127dB at 1m in front of the speaker, 70dB of sound is transmitted throughout the site, Was clearly confirmed.

Table 1 shows the speaker sound pressure and sound reach distance (m) when the speaker terminal voltage was changed using a piezoelectric amplifier with a piezoelectric speaker in which three piezoelectric drivers were attached to a 200 mm x 250 mm x 4 mm honeycomb diaphragm. It is a result.
From this table, an A4 size piezoelectric speaker produced a sound pressure of 127 dB at a terminal voltage of 45 V, and the sound transmission distance was 250 m.

  FIG. 3 shows a piezoelectric speaker network system for the purpose of selectively transmitting necessary information from a center facility to base stations in area units constituting a wide area. Disaster information and criminal information can be selectively transmitted to areas that require it.

  FIG. 4 shows an example of manufacturing a piezoelectric speaker that emits sound from both sides. Piezoelectric vibrators were attached from both sides to two honeycomb diaphragms that were stressed and curved. With this structure, sound with almost the same sound pressure can be emitted omnidirectionally from both sides of the speaker.

  FIG. 5 shows a piezoelectric speaker with a hood attached. Piezoelectric speakers are basically omnidirectional, but some directivity is expressed by attaching a hood.

  FIG. 6 shows measured values of omnidirectional characteristics and distance attenuation, which are main characteristics of the piezoelectric speaker. From the measurement results, it can be seen that sound is omnidirectionally radiated from both sides of the piezoelectric speaker in a substantially circular shape. It can also be seen that the sound pressure distance attenuation is small compared to dynamic speakers.

Piezoelectric speaker network system in local area Distributed piezoelectric speaker system in the area Wide area piezoelectric speaker network system Piezoelectric speaker 1 Piezoelectric speaker 2 Piezoelectric speaker omnidirectional characteristics and distance attenuation graph

1: Piezoelectric speaker 2: Regional area 3: Base station 4: Center facility 5: Frame 6: Honeycomb diaphragm 7: Anti-vibration rubber 8: Piezoelectric driver 9: Hood

Claims (3)

A piezoelectric speaker that radiates sound radially from both sides of the speaker, with two honeycomb diaphragms pulled by bolts, and a plurality of piezoelectric drivers placed symmetrically on the bolt axis of the diaphragm to which bending stress is applied. The piezoelectric speaker network system is distributed so that a circle whose radius is the voice arrival distance is in contact with the area so that sound can be transmitted throughout the area. 2. The piezoelectric speaker network system according to claim 1, wherein the piezoelectric speaker has a hood . 3. The piezoelectric speaker network system according to claim 1, wherein a piezoelectric amplifier that applies a voltage of 45 V or more to a piezoelectric driver of the piezoelectric speaker is used.