What is Echolocation Sound?

Caution: All the articles that I like to share here are meant for newbie only, not for the experts who knew every things already.
And if any of you don't agree, don't criticize me, just ignore it. Don't read any of my article again.
But any sincere and constructive comments with your name are welcome.

We all know that swiftlets used echolocation to see in the dark.
But I think few newbie like me know that the echolocation sound is only the tek, tek, tek sound, not all sounds from swiftlets are used as echolocation sound, not the singing sound, not the crying sound from the baby, not the mating sound, etc.

You all might want to ask the question "How do you know? Can you talk to swiftlet or understand swiftlet?"
I don't know until I saw the attached video.

In the video, an American boy, Ben Underwood, 16 years old, he was blinded since he was 3 years old.
He had cancer in his eyes, doctor advised his mom that unless he had an operation to take his eyeball out, he would die of cancer.
So his mom decided to let him have the operation.

After the operation, Ben told his mom "mom I can't see anymore"
His mom tried to comfort him said "yes, you can see by your hand by touching me, you can see by your nose, you can smell that I am here.
You can see by your ear, you can hear me,....... etc" A very good mom!

One day, one year after his operation, while Ben sat in his mom's car back seat, he asked his mother " mom do you see a big building out there?"
His mom said " yes, I can see the big building out there, do you see the big building out there too?"

We see things around us because of the reflection of light from an object into our eyes.
But Ben and many animals like swiftlet, bat, etc. can see by the reflection of sound from that object into their ears.

Ben can walk anywhere without using a cane or guiding dog as other blind people elsewhere used.
He only used the tek,tek, tek sound similar to the swiftlet's tek, tek, tek sound.
He can ride bicycle, play skateboard, basketball and video game by only using his echolocation tek, tek, tek sound.

He can speak and communicate with others as normal, but those sounds are not functioned as echolocation sound.
Only the tek, tek, tek sound he made is used as an echolocation sound for him to see.

Please watch the rest from the video and understand more about the echolocation sound by yourself.
Enjoy!

http://www.youtube.com/watch?v=qLziFMF4DHA&feature=related

From all the frequency graphs that we saw, can we say that the frequency range of all swiftlet sounds, not just the echolocation sound are between 1-6 kHz.