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This module gives an analysis of the time and frequency domain characteristics of a laugh track. It is part of a larger series discussing the implementation of a real-time laugh track removal filter.

Introduction

A laugh track is a commonly heard part of sitcoms and other comedy shows found on television since the early 1950s. A laugh track can be defined as a prerecorded superposition of samples of people laughing mixed into a television show to "enhance" it. A single laugh track can be composed of a variety of male laughter and female laughter. Often individual, distinct laughs are added in at the end to make laugh tracks sound like the laughter of a live audience instead of simply something generated from prerecorded samples. All of this makes it very difficult to detect a laugh track based on relatively simple heuristics.

Frequency analysis

Looking at the Discrete Fourier Transforms of a laugh track(Fig. 1) and a two minute sample of a television show(Fig. 2), we notice some characteristics of the laugh track such as the slightly larger spike in one of the mid-range frequencies, which is difficult to detect, there is not much difference in the spectrum in the two signals. The spikes we see are also not characteristic of every laugh track, so it would be difficult to create a method of detecting laugh tracks solely by looking in the frequency domain. Factoring in variability such as the dominance of male or female voices in the individual laugh track as well as varying lengths and intensities of a laugh, the problem becomes even more difficult when attempting detection using DFTs and a bandpass filtering scheme.

Tv show sample

Laugh track sample

Time analysis

It is much easier to look for a laugh track in the time domain because the envelope that is characteristic of a laugh track as can be seen in the figure below is much more prominent than the spikes that we see in the DFT of the two signals. This envelope follows the magnitude of a normal laugh track. After a joke, people abruptly start laughing and then the laughter slowly dies down. This is found to be the case in almost every single laugh track instance found in the TV shows that we looked at. Even if a laugh track is short, we can see the same envelope, just compressed more so than in the example. If a laugh track is quieter or louder, we will still be able to see the envelope, though this makes detection based on height thresholds more difficult as regular speech may look very similar to our envelope when a laugh track is shorter and quieter.

Laugh track in the time domain

A laugh track in the time domain, with the characteristic envelope drawn in red on the original waveform.

Conclusion

Other approaches at detecting laugh tracks were also considered, but envelope detection in the time domain proved to be the most effective manner of detecting laugh tracks. Matched filtering and looking for distinctive characteristics in the frequency domain proved to be fruitless. The envelope in the figure above is quite distinctive and relatively easy to detect, even with a fairly simple algorithm, so this approach was used in our detection and removal scheme.

Questions & Answers

where we get a research paper on Nano chemistry....?
Maira Reply
what are the products of Nano chemistry?
Maira Reply
There are lots of products of nano chemistry... Like nano coatings.....carbon fiber.. And lots of others..
learn
Even nanotechnology is pretty much all about chemistry... Its the chemistry on quantum or atomic level
learn
Google
da
no nanotechnology is also a part of physics and maths it requires angle formulas and some pressure regarding concepts
Bhagvanji
Preparation and Applications of Nanomaterial for Drug Delivery
Hafiz Reply
revolt
da
Application of nanotechnology in medicine
what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
Damian
yes that's correct
Professor
I think
Professor
Nasa has use it in the 60's, copper as water purification in the moon travel.
Alexandre
nanocopper obvius
Alexandre
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
Rafiq
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
Damian
How we are making nano material?
LITNING Reply
what is a peer
LITNING Reply
What is meant by 'nano scale'?
LITNING Reply
What is STMs full form?
LITNING
scanning tunneling microscope
Sahil
how nano science is used for hydrophobicity
Santosh
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
Rafiq
what is differents between GO and RGO?
Mahi
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
Rafiq
if virus is killing to make ARTIFICIAL DNA OF GRAPHENE FOR KILLED THE VIRUS .THIS IS OUR ASSUMPTION
Anam
analytical skills graphene is prepared to kill any type viruses .
Anam
Any one who tell me about Preparation and application of Nanomaterial for drug Delivery
Hafiz
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
Bob
The nanotechnology is as new science, to scale nanometric
brayan
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Damian
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
Adin
why?
Adin
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Elec 301 projects fall 2007. OpenStax CNX. Dec 22, 2007 Download for free at http://cnx.org/content/col10503/1.1
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