Voice changers~~~

After so many years of staying in japan,I found something amusing about japanese women when they talk on the phone.
Almost 90% of them will talk in a high tone voice when they are speaking with the other party(phone call).This will occur usually when the other party is a stranger or someone not to well known to her.

In my family too,I listen to my mother in law and my two sisters in law ,speaks when they use or answer the phone..just so funny..their voice automatically change to be like a young girl's voice..so high tone...
But when the phone call is from someone they know too well ,like family members..they will speak with their normal voice..funny right?

At first I thought ,it is only the female members of my family speaking like that..
but I was wrong..in my working place too,almost 90% of the female staff speaks like that when they answer the phone call...

I find this so amusing..as some of these ladies have such low tone when they speak normally,but when they answer the phone..so automatic..the voice pitch is so high tone..unbelievable..hahaha...
I wonder if anyone of you too is speaking like that or not???? (^-^)