Sound on Display Technology

August 18, 2021 - Issue 1

Display-as-a-Speaker (DaaS) Technology

CHALLENGES IN STATE-OF-THE-ART & SOLUTION Introduction Display devices like televisions, smartphones, laptops, tablets, vehicle infotainment systems, or the like, have become an essential part of our daily life. One important module included in these display devices is the speaker module. The speaker module generates audio output corresponding to the content played on the display devices. In the case of smartphones or mobile devices, an additional speaker module is provided to serve as an earpiece to assist users in listening to telephonic conversations.

Challenges One of the prime focuses of the researchers is to ensure the sound output produced by the speaker module is clear and properly perceived by listeners. To achieve this, identifying a suitable location to place the speaker module is one of the first steps and the location in the device is identified such that sound generated/output by the speaker module is directed or focused on the listener.

As illustrated below, in conventional televisions, the speaker modules are either positioned on the side pillars (i.e., left and right side) of the display or below the display. In the case of phones, the earpiece speaker, i.e., the speaker dedicated for hearing the calls is positioned at the top end of the display and the loudspeakers are positioned at the bottom end of the display or the bottom end of the frame. In these conventional designs, the audio quality was decent, as the speakers are mostly forward-firing speakers, i.e., audio waves generated by the speakers are fired directly towards the listener and not getting reflected from any surface. However, the sound emitted from the speaker is not in sync with the visuals, as the location of the visuals does not overlap with the location of the audio output. For example, visuals displayed in conventional television show a singer who is located close to the middle portion of the display and singing a song. Here, in the conventional designs, as the speakers are located at the side pillars, therefore the audio output generated from the sides of the display is not in sync with the visuals i.e., the singer who is shown to be located at the middle portion of the display. This impacts the overall user experience. Additionally, such designs appear bulkier as unnecessary space is occupied in the front portion of the display device by the speaker module and its components. Apart from this, the speaker grills expose the internal circuitry of the device to moisture, dust, etc., which poses an additional challenge especially to portable devices such as phones and PDAs, as ensuring water resistance is an important aspect these days.

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The demand for lighter devices forced the designers to reduce the size of the bezels/frame and with the bezels becoming thinner, the designers are bound to remove the speakers from the front portion, i.e., sides or top/bottom of the display of the devices, especially in case of television. Thus, the speaker modules are placed either behind the display panel (with a cone of the speaker facing towards the backside, i.e., wall) or at the bottom of the display panel.

In both cases, the sound waves generated by the speakers are not received directly by the listener, instead, the sound waves reach the listener after getting reflected from the back wall or the floor. The audio quality gets further deteriorated.

Solution The simple solution to the above problems is Display-as-a-speaker technology.

The technology enables the entire display panel to act as a speaker. Unlike conventional speaker-based devices, where a paper or a membrane is vibrated to output sound. Here the entire display acts as an oscillator and generates sound. One or more actuators/transducers are deployed to drive the display screen to produce sound in an audible frequency band, i.e., 20 Hz to 20kHz. In the display-as-a-speaker technology, the display panel itself vibrates and generates sound waves, thus the generated sound waves are fired directly towards the listener/audience. The listener receives the audio directly without getting reflected from the back wall or bottom surface and this ensures that the listener hears clear audio.

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Further, the audio output is synchronized with the visuals as the audio output is produced by the display itself. The technology offers an immersive audio experience, i.e., audio appears to originate from the visuals of the display itself. Let us consider visuals show a news anchor located at the center of the display and the news anchor is delivering the news. Here, the display itself vibrates and produces sound such that the audience perceives that the audio is originating from the center of the display itself Not from any other location such as the bottom or the sides of the display. Thus, the audio output is synchronized with the visual content.

In the case of smartphones and PDAs, since the entire display acts as a speaker, therefore no speaker grill or cutout is required in the display, which assists in making the device water/moisture-proof and dustproof. Additionally, no dedicated space is required to house the earpiece which further allows the designers to reduce the bezels and design a bezel-less display.

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