The materials you could use to make DIY headphones are the following:
Headband - A headphone has a headband used to put over your head. You can use a normal headband for this.
Small Tin Cans - This can be used for the housing of the speaker.
Foam - The speaker has earpads. You can use foam for this.
Wire with jack - You can use a wire with a jack from an old broken earphone or headphone.
Speakers - This one is hardest and the most important part of the headphone. You can look up how to make one using magnets and copper wire or you can just recycle an old pair of working speakers that fit in tin can housing.
Answer:
Telephone conversation
Explanation:
Any real time conversations are synchronous.
Answer:
I use Wikipedia to know anything
