Skip to content Skip to navigation

Connexions

You are here: Home » Content » Algorithm Overview

Navigation

Lenses

What is a lens?

Definition of a lens

Lenses

A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual Connexions member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

This content is ...

Affiliated with (What does "Affiliated with" mean?)

This content is either by members of the organizations listed or about topics related to the organizations listed. Click each link to see a list of all content affiliated with the organization.
  • Rice University ELEC 301 Projects display tagshide tags

    This module is included inLens: Rice University ELEC 301 Project Lens
    By: Rice University ELEC 301As a part of collection:"ELEC 301 Projects Fall 2007"

    Click the "Rice University ELEC 301 Projects" link to see all content affiliated with them.

    Click the tag icon tag icon to display tags associated with this content.

Recently Viewed

This feature requires Javascript to be enabled.

Tags

(What is a tag?)

These tags come from the endorsement, affiliation, and other lenses that include this content.

Algorithm Overview

Module by: Blake Brogdon, Thomas Deitch, Kyle Barnhart, Britt Antley. E-mail the authors

User rating (How does the rating system work?)
Ratings

Ratings allow you to judge the quality of modules. If other users have ranked the module then its average rating is displayed below. Ratings are calculated on a scale from one star (Poor) to five stars (Excellent).

How to rate a module

Hover over the star that corresponds to the rating you wish to assign. Click on the star to add your rating. Your rating should be based on the quality of the content. You must have an account and be logged in to rate content.

:
(0 ratings)

Algorithm Overview

The first step in detecting a signal is to input it into the system. Since we are using an audio signal, a microphone is the obvious choice. However, the desired control signal is not the only sound in the room. There is also the music that is being played through the speakers as well as outside noise. Unfortunately, there is not much that can be done about the random noise that is present in the room. However, there are tools available that allow us to minimize the interference caused by the music. Specifically, we can use an adaptive filter to mimic the room’s effect on the output of the sound card, providing us with an estimate of the music’s contribution to the signal received by the microphone. We can subtract the microphone’s signal from this estimate in order to obtain—hopefully—only the whistle.

Figure 1 shows the block diagram of our system. All of these components fall into four main categories:

  1. Signal acquisition
  2. Whistle isolation
  3. Whistle frequency analysis
  4. iTunes interface
The acquisition phase is the top portion of the diagram, the whistle isolation system is represented by the ĥ box and the band pass filter, the rest of the diagram (except for the Java controller) comprise the whistle analysis phase, and the Java controller is the iTunes interface.

Figure 1: In our system, the sound is output through the speaker, and the microphone receives the music and whistles while the sound card receives the audio without the room affecting it. We then remove the music and process the whistle.
Our System's Block Diagram
Our System's Block Diagram (graphics1.png)

After isolating the whistle, we apply a band pass filter whose pass band corresponds to common whistle frequencies in order to remove extraneous noise outside of these whistle frequencies.

We then take the Short Time Fourier Transform in order see how the frequency components of the whistle change over time. If the frequency of the whistle is increasing iTunes should advance to the next track, and a decreasing frequency will skip to the previous track. To accomplish this, we examine the frequency with maximum power (the argmax in the figure below) and accumulate several readings of this frequency. In order to see if this function is increasing or decreasing we take the derivative and examine its average value. If the average value is positive, the function must have been increasing and the whistle must have been from high to low frequencies.

Content actions

Give Feedback:

E-mail the module authors | Rate module ( How does the rating system work?)

Rating system

Ratings

Ratings allow you to judge the quality of modules. If other users have ranked the module then its average rating is displayed below. Ratings are calculated on a scale from one star (Poor) to five stars (Excellent).

How to rate a module

Hover over the star that corresponds to the rating you wish to assign. Click on the star to add your rating. Your rating should be based on the quality of the content. You must have an account and be logged in to rate content.

(0 ratings)

Download:

Module PDF

Add module to:

My Favorites (?)

'My Favorites' is a special kind of lens which you can use to bookmark modules and collections directly in Connexions. 'My Favorites' can only be seen by you, and collections saved in 'My Favorites' can remember the last module you were on. You need a Connexions account to use 'My Favorites'.

| A lens (?)

Definition of a lens

Lenses

A lens is a custom view of Connexions content. You can think of it as a fancy kind of list that will let you see Connexions through the eyes of organizations and people you trust.

What is in a lens?

Lens makers point to Connexions materials (modules and collections), creating a guide that includes their own comments and descriptive tags about the content.

Who can create a lens?

Any individual Connexions member, a community, or a respected organization.

What are tags? tag icon

Tags are descriptors added by lens makers to help label content, attaching a vocabulary that is meaningful in the context of the lens.

| External bookmarks