Published online by Cambridge University Press: 06 July 2010
Our first encounters with signals were in the time domain for 1-D signals and the spatial domain for 2-D images. We have seen time domain signals as a graph or as a trace on an oscilloscope. Undergraduate engineers have usually used a spectrum analyzer in the laboratory to characterize signals in the frequency domain. However, almost everyone has seen a graphical representation of an acoustic frequency spectrum when they observe the flashing lights on the spectrum displays of graphic equalizers on higher quality stereo systems. The display shows the observer the relative power of the signal in various frequency ranges.
The interpretation in the frequency domain of audio signals is aided by the fact that the ear is basically a spectrum analyzer. It is easy to interpret the terms high and low frequency when applied to audio signals. We have no difficulty thinking of a rumble as a low-frequency sound, or a screech as a high-frequency sound.
We will have to work a bit to achieve the same associations of visual phenomena with frequency bands. However, be assured that the effort is worthwhile. Among the interpretations that will be shown are that edges are associated with higher frequencies; shading is associated with lower frequencies; blurring is basically a low pass filter, while differentiation is a high pass operation.
To save this book to your Kindle, first ensure no-reply@cambridge.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Find out more about the Kindle Personal Document Service.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.
To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.