Here's how Note 10 may use Sound on Display tech to get an 'all-screen' design

LG has a similar tech called Crystal Sound that it has already pioneeringly employed on the LG G8, Sony's had its Acoustic Surface for a while on TVs, too, and Huawei just employed its Acoustic Display Technology on the P30 Pro. 

In fact, as early as last year's MWC expo in February, we were able to play around with the Vivo APEX concept that then turned into the Vivo NEX retail phone, and, while its signature feature at the time was the finger scanning that worked over half of the display, the Screen SoundCasting technology was already present as well. 

Here it is on the retail NEX, in the from of a small actuator glued to the back of the OLED panel, sending its electromagnetic impulses directly to the panel which ripples the air above it to deliver the sound vibrations to your eardrum.

First off, you need an OLED display to place small exciters/actuarors behind. The LCD panels have an extra backlight layer that can't transfer the tiny electromagnetic vibrations that the exciter pumps through the screens, using the top layers as a speaker diaphragm of sorts. 

When we talk about speakers, you are probably imagining those cone-shaped diaphragms that sit atop a magnetic gap between them and the voice coils. Diaphargms needn't be cone-shaped, though, the sheer nature of vibrations produces enough of an air ripple effect to emit sounds, and that's exactly what those tiny actuators behind the displays of the G8 or P30 Pro are meant to do. 

The P30 Pro actually has two circular ones looking like watch batteries - the larger ones to emit the conversation from the top of the screen where an earpiece would be, and the smaller one to vibrate for notifications and such, a pretty clever setup.

Samsung's own Sound on Display technology works in a similar fashion - a tiny actuator or two behind the AMOLED displays. The humble Galaxy A60/M40 are the ones where this Samsung technology employed first, and this, coupled with their punch-hole display designs makes them achieve an "all-screen" front similar to its much more expensive brethren in the Galaxy family. They use just one tiny exciter behind the AMOLED display, as you can see in the screenshot from the disassembly video below. 

Samsung, however, doesn't advertise this as Sound on Display, but just says Screen Sound Technology, and with a good reason. They do have speakers inside, and the tiny screen exciter motors make the top of the display vibrate only during voice calls, as you can see in the disclaimer below. Whether or not this will be the case on the upcoming Galaxy Note 10, remains to be seen.