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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

anyone know any internet site where one can find nanotechnology papers?
Damian Reply
research.net
kanaga
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
Maciej
characteristics of micro business
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
s.
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
Tarell
what is the actual application of fullerenes nowadays?
Damian
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
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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