What is Echo: Definition and 37 Discussions

In audio signal processing and acoustics, echo is a reflection of sound that arrives at the listener with a delay after the direct sound. The delay is directly proportional to the distance of the reflecting surface from the source and the listener. Typical examples are the echo produced by the bottom of a well, by a building, or by the walls of an enclosed room and an empty room. A true echo is a single reflection of the sound source.The word echo derives from the Greek ἠχώ (ēchō), itself from ἦχος (ēchos), "sound". Echo in the Greek folk story is a mountain nymph whose ability to speak was cursed, leaving her able only to repeat the last words spoken to her. Some animals use echo for location sensing and navigation, such as cetaceans (dolphins and whales) and bats.

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  1. Wrichik Basu

    Changing proxy server for WiFi in Amazon Echo Dot and Fire TV Stick

    One of my relatives has an Amazon Echo Dot and a Fire TV Stick. Both are connected to the same WiFi. Recently, their internet provider changed the proxy settings such that the default proxy no longer works. They have provided a set of proxies that can be used instead. We have manually set those...
  2. P

    I If I clap once to a wall, and then walk forward, will I hear an echo?

    This is a diagram: ------------ reflective wall X --> Y I stand at position X and clap towards a reflective wall. Theoretically, could I walk to some point Y, where there is constructive interference between my clap and the reflected clap, resulting in my hearing a much louder sound. Is...
  3. binbagsss

    MATLAB Matlab: echo generator question

    The task is to given an input column vector (with values between -1 and 1 representing the digitized data), fs the sampling rate, delay to represent the delay of the echo in seconds, amp specifying the amplification of the echo, to add this echo to the original signal after delay seconds. Other...
  4. Y

    MRI Spin echo sequence and STIR

    I would like to ask a question about MRI Spin echo sequence. after first 90 degree RF pulse, the free induction decay occurs. And 180degree refocusing pulse is given again. And echo signal is obtained at TE. My question is that is the the signal highest when the protons are back again in...
  5. Simon Peach

    B Exploring Echoes of Electromagnetic Wave Lengths

    In the electromagnetic wave lengths say from x-rays to the 21 cm hydrogen line, the wave has a wave length. When it hits a receiver, eye, camera sensor whatever, it is turned into an electrical signal that can be interpreted by that device. Now we get to my question, is there an echo of that...
  6. J

    Pulse echo technique to find the distance of the Moon

    Homework Statement [/B] Over 40 years ago, the Apollo astronauts placed reflectors on the surface of the Moon. These are still used by a number of observatories on Earth to monitor the distance to the Moon by reflecting pulses of laser light from them and detecting the reflected signal...
  7. R

    When does a sound echo not disturb its listener

    Homework Statement :[/B] At a prayer meeting the disciples sing JAI RAM .The sound amplified by a loudspeaker comes back after reflection from a building at a distance of 80 m from the meeting. What maximum time interval can be kept between one JAI-RAM and the next JAI-RAM so that the echo...
  8. J

    I T2 relaxation and Spin Echo of protons

    I’ve been reading on the physics of how a Magnetic Resonance Imaging (MRI) works from this link regarding the T1 and T2 relaxation time of protons. So far I understand the concept except what they’re trying to explain in the last 2 paragraphs about spin echo. This is what I got from these last...
  9. A

    What do echo and reverbation have in common?

    Homework Statement What do echo and reverbation have in common? Homework Equations We can hear sounds with a difference of 0.1 seconds. Speed of sound 340 m/S. the distance the sound travels is 34 m. the distance from the wall is 17m. The Attempt at a Solution They are the reflection of sound...
  10. Xoloti

    Train Whistle Echo: Calculating Distance & Temperature Effects

    Homework Statement a)a stationary railroad whistle is sounded. An echo is heard 4.0 seconds later by a train's engineer. If the speed of sound is 343 m/s, how far away is the reflecting surface? b) If the temperature of the air increased, how would this change your answer? Homework Equations...
  11. SpicyWassabi101

    Solve Physics Echo Problem: Air Echo Returns 1.33s Later

    Homework Statement A boat is floating at rest in dense fog near a cliff. The captain sounds a horn at water level and the sound travels through the salt water (1470 m/s) and the air (340 m/s) simultaneously. The echo in the water takes 0.40s to return. How much additional time will it take the...
  12. B3NR4Y

    Calculating Distance Traveled by a Honking Car and Echo

    Homework Statement A car is traveling with a constant speed v on a straight road which forms an angle α with nearby straight wall. When the car is at a distance l from the wall the driver presses the horn briefly. What distance would the car have traveled (from the spot of the honk) when the...
  13. B

    Difference between sound echo and mirror reflection

    Homework Statement Why is is that when we look in a mirror we expect to see a reflection equally as bright as the real image, but when we stand in front of a cliff and clap our hands we don't hear an echo as loud as the original sound? Homework Equations R = (z2 - z1)/(z2 + z1) The Attempt at...
  14. K

    Is there even a scientific reason for this

    So this is what happened. the thing is that wherever i go i hum. So i was in the bathroom that day and it was as usual tiled everywhere. So when I started to hum, it echoed. Nothing special about it. But as i raised my pitch, there was a pitch at which my humming sound echoed ENORMOUSLY. And...
  15. R

    How long will it take for the echo to return

    Homework Statement A submarine sends out a sonar wave that has a frequency of 545 Hz. If the wavelength of the sound is 2.60 m, how long does it take for the echo to return when the sound is reflected from a submarine that is 5.50 km away? Homework EquationsThe Attempt at a Solution i...
  16. R

    Calculating the Distance of a Sonar Echo

    Homework Statement A sonar echo returns to a submarine 1.10s after being emitted. What is the distance to the object creating the echo? Homework Equations rate X time = distance The Attempt at a Solution( 1533m/s X 1.01s) divided by 2 = distance
  17. N

    PHP HTML and PHP issue: display HTML form variables using PHP echo

    Heeeeeeellllllllllllllooooooooooooo, I have a question about HTML and PHP: Firstly, I am using Apache2 and PHP5 (I think) and running it as a localhost. I created a simple HTML form that sends the variables via post to a PHP file; there are two variables with the names "nickname" and...
  18. jegues

    Signals unit impulse response h(t) ECHO

    Homework Statement a) Find the unit impulse response h(t) of an audio system that causes two echoes, one occurring at 0.5 seconds and the other one at 1.5 seconds. Please sketch H(w). (Magnitude and phase) b) Design a system that can eliminate noise coming from the 60Hz power signal (thus...
  19. S

    Distance of building related to echo

    Homework Statement A road lies between two parallel buildings. A motorist travels with speed 36 km/h on the road and hits the horn. He heard the echo 1 second later. The speed of sound is 330 m/s a. Find the distance of the building b. When will he hear the second echo? Homework Equations...
  20. Z

    [BASH] Possible to echo only certain range of WORDS in a string?

    Hi, I'm new to Bash scripting and I need some help with this: I need to echo only a specified range of words from a string based on index; so for example if I had: a="hello how are you today" Is there a way to echo only "how are you" by specifying the index 2 to 4? (in one line...
  21. F

    Cause of echo in VoIP conversation

    Hello Forum, it can happen that in a VoIP conversation we hear some echo, i.e. we hear our voice, with a certain delay... We speak and the signal goes to the receiving party. Why would a copy of our voice signal make a round trip and come back to us? What causes that "reflection" of the...
  22. A

    Find difference in echo times, doppler shift?

    Homework Statement A bat is pursuing an insect, and using echolocation of 41 kHz sound waves to track the insect. The insect is initially 34 cm from the bat but then moves to a distance of 44 cm as it tries to escape. What is the difference in the two echo times that the bat measures...
  23. M

    How to find distance given echo time. (WAVES)

    Homework Statement A ship is 220metres from a large cliff when it sounds its foghorn. If the echo time is 0.5s, how far is the ship from the cliff? Homework Equations Distance=220m Echo time= 0.5s The Attempt at a Solution 220*0.5= 110 m I really don't know.. Help please
  24. T

    How Do Echo Timings Help Calculate Cliff Distances?

    Homework Statement A cowboy stands on horizontal ground between two paral- lel vertical cliffs. He is not midway between the cliffs. He fires a shot and hears its echoes. The second echo arrives 1.92 s after the first and 1.47 s before the third. Consider only the sound traveling parallel...
  25. D

    Comp Sci What is the Best Way to Create a Secure Password Prompt in C++?

    Homework Statement Currently using stdio.h, conio.h, string.h, stdlib.h not using iostream, namespace std etc. I am asked to make a password prompt where each character echoes an asterisk (*) The user must be able to backspace and delete to make corrections. The password is then...
  26. W

    Determining the distance of a pipe by the length of an echo

    How could I determine the length of a pipe by playing a certain frequency into it, then measuring how long the echo is audible?
  27. M

    MATLAB HELP: We need expert matlab programmer for our echo suppression algorithm.

    Hello we are currently doing our thesis about echo suppression. We already have the algorithm but we don't have any directions on how we can start with our MATLAB program. It's going to be a lot of DSP stuff. we would be glad to pay you if you could help us out/make our program. Our algorithm is...
  28. T

    Calculating Well Depth with Doppler & Echo Effects

    Homework Statement An alarm clock has been thrown down a well. around 100m deep well an alarm clock with a frequency of 368hz sounds for 3 seconds accelerating at 9.8 m/s2 initial velocity 0 Homework Equations How deep is the well? using doppler take in consideration of the echo...
  29. R

    Distance between earch and the echo of the Tycho Supernova

    Is there a known distance between Earth and the dust/gas that the light was reflected from for the supernova of SN 1572 (Tycho's supernova)? I need this calculation to be made without adding the distance to SN 1572 to the time between Tycho's observation and now. Also, what's the angle between...
  30. Simfish

    Dennett and his Echo Chamber Hypothesis

    Sweet Dreams pg. 168-170 "Episodic memory is not for free. One idea is that it is the very echoic power that makes episodic memory possible. Animals remember thanks to multiple repetitions of stimuli in the world. We remember, it seems, one-shot, but really, it isn't just one-shot. What we...
  31. B

    Radar echo and clock synchronization

    Please help me in the folowing problem: It is well known that the radar echo (police radar) establishes a relationship between the period T(e) at which a stationary observer emits successive light signals and the period T(r) at which he receives them back after reflection on an object that...
  32. A

    Submarine echo physics problems

    Homework Statement A submarine on the ocean surface gets a sonar echo indicating an underwater object. The echo comes back at an angle of 20* above the horizontal and the echo took 2.32s to get back to the submarine. What is the object's depth? Homework Equations delta of theta =...
  33. marcus

    Kodama means echo or spirit of the trees

    Kodama means "echo" or "spirit of the trees" I just thought you might like to know :smile: AFAIK the Kodama state was first written in 1988 by Hideo Kodama It seems the Japanese have what they call "clans" and there is a Kodama clan. There have been other famous Kodamas besides Hideo...
  34. M

    Ocean Depth at 7.07s Echo Time - 1.22311 km

    A geological survey ship mapping the floor of the ocean sends sound pulses down from the surface and measures the time taken for the echo to return. How deep is the ocean at a point where the echo time (down and back) is 7.07 s? The temperature of the seawater is 25°C. Find the answer in km...
  35. E

    Solve the Stone Drop Problem: Acceleration of 9.8m/s^2

    i need help on the following problem: "carol drops a stone into a mine shaft 122.5 m deep. How soon after she drops the stone does she hear it hit the bottom of the shaft?" i know that the acceleration is 9.8m/s^2 but i can't use it as speed in the speed=distance/time equation please help me...
  36. L

    News: An ECHO of Black Holes

    An ECHO of Black Holes Sound waves in a fluid behave uncannily like light waves in space. Black holes even have acoustic counterparts. Could spacetime literally be a kind of fluid, like the ether of pre-Einsteinian physics? By Theodore A. Jacobson and Renaud Parentani When Albert Einstein...
  37. T

    Why a duck's quack doesn't echo

    A duck's quack doesn't echo, and no one knows why. Can physics explain this fact and how?