Vertical drive technology generates sound waves by means of vibrations created by an actuator mounted on the end surface of a diaphragm. Its key feature is the fact that sound is emitted in a vertical direction relative to the direction of vibrations produced by the actuator. Sony has used this principle in its Sountina speaker system, which works by vibrating the end surface of a cylindrical diaphragm, instantly propagating compressional waves along the length of the cylinder. These compressional waves apply force to the cylinder in a diametrical direction (vertically relative to the length of the cylinder) according to Poisson's ratio (*) of the solid. This force produces vibration in a diametrical direction, thereby emitting sound from the entire surface of the cylindrical diaphragm.

* This is the ratio between the extension or contraction that occurs along the direction of force applied to an elastic object, and contraction or extension occurring in a direction vertical to the direction of force.

The following provides an analysis of vibration modes on the diaphragm to explain vibration levels. The colors used to represent the vibration levels indicate the amplitude radially throughout the diaphragm. Figure 2 shows the result when a 5KHz sine wave (*) signal is used to vibrate the diaphragm through multiple vibrators. In this case, an analysis of vibration levels shows that amplitude is greatest in a diametrical direction, especially around vibration points, and that vibration does not spread throughout the entire diaphragm. As shown in Figure 3, however, if vibration is caused under the same conditions by actuators on just the end surface of the diaphragm, it spreads evenly throughout the entire diaphragm.

Sony wanted to use this drive technology to vibrate the diaphragm efficiently and produce high-quality sound. It achieved this by developing a new actuator with excellent responsiveness and the ability to produce large stresses. By using vibration analysis simulations and Sony's independently-developed audio materials measurement technology, Sony was able to select the optimal shape and materials for the diaphragm.

* This is the name of the waveform. Others include alternating wave form and pulsating waveform.

1. Use of Linear Source to Reduce Sound Pressure Attenuation

Because the Sountina system uses vertical drive technology to spread vibrations throughout the diaphragm, sound radiates from the entire cylindrical diaphragm, which functions as a linear source measuring one meter in length. Conventional speakers have point sources and radiate sound spherically (up, down, left, right). By radiating sound in a cylindrical pattern, a linear source allows sound to spread out horizontally while limiting vertical spread. This reduces sound pressure attenuation over horizontal distance, with the result that there is less sound level variation according to the distance from the speaker. Furthermore, because vibration occurs across the entire surface of a diaphragm measuring approximately one meter in length, the listener can enjoy the same kind of audio experience no matter where they happen to be in the room and regardless of ear height or listening position.

2. 360° Three-Dimensional Sound Effect with a Sense of Depth

Sountina produces three-dimensional sound with a sense of depth anywhere in a 360° span. This performance, not possible with conventional stereo technology, is achieved by positioning multiple actuators on the end surface of an organic glass diaphragm and using a digital signal processor (DSP) and proprietary signal processing technology to drive each actuator. These audio effects allow a single cylindrical speaker to produce a unique 360° acoustic field. That is why the Sountina system is known as a "Circle Sound Stage."

As shown in Figure 2, the drive technology used in conventional speakers requires the positioning of a drive system on either the front or rear side of the diaphragm. With the vertical drive system, only the end surface of the diaphragm is vibrated and it is not necessary to place driver devices on either the front or rear sides of the diaphragm. This characteristic offers new design opportunities, including the use of transparent diaphragms.

Sony's Sountina system uses transparent organic glass tubes to create speaker designs that are totally different from conventional designs. In addition to continued efforts to expand the existing audio market, Sony also aims to build new markets by developing new applications for its vertical drive technology and creating attractive new products.