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What is Echo in Audio? – Understand Its Effects!

You definitely have experienced this phenomenon before, especially in large and empty rooms. It is a natural occurrence in our lives, but many people may often overlook its complexity. However, if you aspire to be a professional in the audio engineering industry someday, you just have to find out what is echo in audio!

The concept of today’s subject is not too complicated to understand. But you might be surprised at the amount of details that you may never have considered. Ultimately, there are various factors that affects the function of echoes, and how they are perceived by the human ear. Well, without further delay, let us uncover its secrets!

Echo – Cool Sounds!

In the discipline of acoustical engineering, an echo is defined as a reflection of sound that arrives at the listener with a delay after the original sound. The distance of the reflecting surface from the sound source and the listener, will have a direct impact on the level of delay. Echoes are commonly heard being produced by a building, the walls of an enclosed room, or an empty room.

Echo Diagram

Diagram illustrating how echo actually works / Photo by MingTsang Lin / CC BY-SA 4.0

Humans are not the only ones who could hear echo, and even some animals such as cetaceans (dolphins and whales) and bats, instinctively rely on echo to sense their location and navigate through their environments. Interestingly enough, in Greek folklore, “Echo” is a mountain nymph who had her speech ability cursed, and she can only repeat the last words anyone spoke to her.

Let us go through the list of topics for today:

  • Acoustical principles
  • Creative applications
  • Famous echoes

Acoustical Principles

Sound waves are often reflected off walls and other hard surfaces. The reason for reflection may be explained as a discontinuity in the propagation medium. An echo can distinctively be heard when the reflection returns with enough intensity and delay. A “reverberation” happens when sound, or the echo itself, is reflected multiple times from multiple surfaces.

Animal Echo

A depiction of the ultrasound signals emitted by a bat, and the echo from a nearby object

An echo cannot be distinguished (from the original sound) by the human ear, if the delay is less than 1/15 of a second. Sound waves in dry air, travels at an approximate speed of 343 m/s at a temperature of 25 °C. Hence, for an echo to be perceived by a person located at the sound source, the reflecting object must be more than 17.2m from the sound source’s position.

Theoretically, when an echo is produced by a sound in two seconds, the reflecting object is 343m away. Echoes can also be experienced in nature, especially in natural settings such as canyon walls or rock cliffs facing water. The strength of echo is often measured in dB sound pressure level (SPL). Echoes can be useful (as in sonar) or unwanted (as in telephone systems).

Creative Applications

Ever since the 1950s, electric echo effects have been incorporated into music recordings. Mike Battle designed the “Echoplex” in 1959, that recreates the sound of an acoustic echo. The Echoplex was then used by some of the most notable guitar players in the 60s, and has set the standard for echo effects in that era. Original Echoplexes have great value and are highly sought after.

Echoplex

The Maestro Echoplex EP-2 (Tube Tape Echo) / Photo by evan p. cordes / CC BY 2.0

Echoplexes were not only very popular among guitar players (and also some notable bass players such as Chuck Rainey, or trumpeters, such as Don Ejudvntfhllis), as many recording studios have used them as well. Starting from the 70s, Market built the solid-state Echoplex for Maestro and in the 2000s, most echo effects units use electronic or digital circuitry to recreate the echo effect.

Famous Echoes

Some of the most well-known locations for echoes are as follows:

  • Hamilton Mausoleum, Hamilton, South Lanarkshire, Scotland: Its high stone holds the record for the longest echo in the world, taking 15 seconds for the sound of a slammed door to decay.
  • Gol Gumbaz of Bijapur, India: Any whisper, clap or sound gets echoed repeatedly.
  • The Echo Wall at the Temple of Heaven, Beijing, China
  • The Whispering Gallery of St Paul’s Cathedral, London, England, UK
  • Echo Point, the Three Sisters, Katoomba, Australia
  • The Temple of Kukulcan (“El Castillo”), Chichen Itza, Mexico
  • The Baptistry of Pisa, Pisa, Italy

That’s all I have for you folks today. Do you just love listening to echo effects? Or personally find them rather annoying?

Let me know your thoughts down below, and do share this article with your pals!

Farhan

When I'm not rocking out to great music, I'd prefer to be sleeping on a field on a windy day =)

4 Comments

  1. I must admit, Echo (or Delay in the production world) is something I hear and use on a daily basis. Adding it to a vocal track is almost like the cherry on top and adds so much depth to a flat or, otherwise, bland vocal. It’s become my own personal cheat to cover up a bad singer.The monuments you mentioned should at least be heritage sites, don’t you think? Anything that can naturally hold an echo for 15 seconds should be preserved.

    • Hey Ryan!

      Yeah, echo effects if used tastefully, can get you some really interesting sounds. Its great to know that you have used them successfully in your own projects. I also do agree with you on preserving the “echo” sites. We wouldn’t want our future generations to miss out on experiencing them first hand.

      Thanks for your thoughts!

  2. Hello Farhan,

    I wonder echo plays a part on news where one was broadcast inside a studio and the other was stream lived on a particular site. You mentioned that echo is unwanted in telephone system. Could this impact all means of telecommunication in general? I mean, when we watch the news, the receiver took a second or two to react and respond after the studio broadcaster asks the questions.

    • Hello Tar!

      I understand where you are coming from with regards to broadcasting. However, the situation that you describe, probably has nothing to do with echo. Broadcasting engineers may intentionally delay the “live” signal for various purposes, such as to prevent profanity or bloopers.

      On the other hand, when broadcasting across a distance, data needs to be compressed and it is buffered for this purpose. The buffer is a certain size, say 5 seconds at a time. When broadcasting live, this buffering can cause overhead in the processing of the signal and can cause the signal to be delayed.

      In most cases this is unnoticeable due to modern technology. However when a reporter is on location they don’t always have access to equipment to be able to stream without delay.

      Hope that answers your question. Thanks!

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