Can Loudspeaker reproduce very high freuency?

Very probably not. No matter what quality, it's still a single, general purpose speaker which will be limited in frequency response. And they don't even try since it's a rare person that can even hear 22,000 Hz, and most are limited closer to 18,000, even just 16,000 Speakers that can faithfully reproduce frequencies near 20,000 hz are actually speaker SYSTEMS that consist of multiple components, notably a tweeter that can respond that high, plus a cross-over network to direct only those frequency ranges to the appropriate components.

That's a LOT of incredible expense to incorporate into a phone, not to mention the complete lack of room to do it.

NO, phone company cut off the phone line frequency about 4000 Hz (most human voice frequency) to save its line bandwidth. Therefore, you never hear any high tone music able to transmit through telephone line. The small built-in speaker of your phone could reproduce not more than 12000Hz, because that is the limitation of that type of speaker.

Chances are extremely unlikely that they can do this. Most amplifiers have a filter on the input that cuts off very low and very high frequencies. Even if it could, the only way you would know if this is actually happening is if you had an oscilloscope that could read that sort of frequency.

This is because the average human cannot hear above 16000 Hz.

What are you going to do, play music for your dog. Chances are you can't hear anything higher than 18,000 Hz.

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