Digital Audio & Technology Application

SamplingQuantization

Digital RecordingReproduction Process

Disk Based Audio System

By Azmawati Binti Mohd Lazim | azmawati@mmu.edu.my

Learning Objective

• LO1 - To execute audio recording sessions in a proper studio environment.

• LO2 - To operate the features found in a digital audio workstation and essentially use it as a tool for multimedia production.

What is sampling?

The term 'sampling'

used in music

production

which is taking

'samples' (or parts)

of an existing music-piece and

using that to create

a new music

production.

converting analogue sound to digital

soundfiles

The act of capturing an

amplitude value is what is called

‘Sampling’.

A sample is actually a

static representati

on of a waveform in

time.

The amount of samples

that are taken per second is

what’s called the

samplerate.

Real life situation

If we sample a 20 KHz frequency

with a samplerate of

20KHz, we only have one

sample per cycle.

To capture the +ve and -ve side of the cycle we

will need to have a sampling rate that is double the frequency

that we’re sampling. 

In other words : To

capture a 20 KHz

frequency, we’ll need to

have a samplerate of

at least 40KHz.

Nyquist Theory

• FS = 2 x FN

• FS=Sampling frequency

• FN=Nyquist frequency 

What is quantisation?

Sampling is capturing an amplitude value in time. This value is captured in a process called quantisation

• As well as with the time axis, digital systems have a certain resolution on the amplitude axis

• The higher this resolution is, the more accurate the digital representation of the waveform’s amplitudes. 

Reproduction ProcessThe higher the bit-depth, the more dynamic range can be captured. So a 24 bits system has a higher resolution than a 16 bits system.

You can imagine that mixing with audio that has a 24 bit resolution is much easier and pleasant to mix with since we literally have more values on the

amplitude axis.

Digital Recording

44.1 KHsamplerate?

Disk-based Audio System

This sample-rate standard dates back to the days of

videocasettes. 

Digital audio was stored in the scans

of a videoframe and a samplerate of 44.1KHz could

fit in both systems.

It was mathematically compatible with both European

PAL as the United States

standard NTSC film systems.

Does Bitrate Really Make a Difference In My Music?

Lossy• MP3• WMA

Lossless• WAV• AIFF

Digital Audio Format: Lossy Format

Both WAV & AIFF file are

uncompressed formats

They are exact copies

of the original

source audio.

The same quality; they just store the

data a bit differently.

AIFF vs WAVAIFF is made by Apple, so you

may see it a bit more often in

Apple products

WAV is pretty much universal.

However, since they're uncompressed, they take up a lot of unnecessary space. Unless you're editing the audio, you don't need to store the audio in these formats.

Digital Audio Format: Lossless Format

MP3, FLAC, MWAMPEG Audio Layer III, or MP3 for short, is the most common lossy format around. So much so that it's become synonymous with downloaded music. MP3 isn't the most efficient format of

them all, but its definitely the most well-supported, making it our #1 choice for lossy audio.

MP3, FLAC, MWAFLAC is Free Lossless Audio Codec with high audio quality and smaller file size. Therefore, it is quite popular with storing FLAC files with less space and better quality and many people have FLAC files.The popularity of

Apple devices like iTunes, iPhone, iPod, Apple Watch

MP3, FLAC, MWAWindows Media Audio (WMA) is an audio data compression technology developed by Microsoft. The name can be used to refer to its audio file format or

its audio codecs. It is a proprietary technology that forms part of the Windows Media framework.

Real Life Situation• Originally,

Microsoft claimed that WMA files had the same quality as MP3 files with half the size

Real Life Situation• Independent

testing has disputed this claim, but WMA may still have slightly better quality than MP3.

So why convert WMA files to MP3?

It is about compatibility

• The most important is compatibility.• Even though WMA is popular in Windows

programs, there are still many multimedia programs and MP3 players that are incompatible with this format.

• MP3, on the other hand, is so ubiquitous that almost any program or device will play it.

• Another reason to convert WMA to MP3 is if the file will be used on Mac-based software.

• https://www.youtube.com/watch?v=sZBjWyyHoO0

So why not 40 KHz you ask?

Common samplerates that are used nowadays can be a bit higher than 44.1

KHz.

Not only does this mean we

can theoretically record higher frequencies,

It also means we have much more samples that are

taken to represent our

audio.

Many operating systems and

audio interfaces

nowadays can support

sampling rates up to 96 KHz or even 192 KHz giving much

higher quality and processing

options.

Good Tips!Working on higher sample-rates.  There’s a number of reasons why we could chose to work with higher sample-rates and bit-depths when recording and mixing. • The first would be the better quality

and more dynamic range given at these higher sample-rates and bit-depths. This is much more pleasing to work with during mixing. KHz for surround material.

Good Tips!Working on higher sample-rates.  • Processing is much more accurate on higher

resolution material. Equalizing, reverbs, filters, etc.

• All sounds much better on higher sample-rate material. This is the reason why many plugins use so called ‘upsampling’ techniques to internally work at higher samplerates when processing audio.

• When you’re producing sound for DVD’s, which can handle samplerate’s up to 192 KHz on stereo material, and 96

Here is a list of most common sample-rates found in the

industry.Samplera

te Usage

44.100 hertz Audio cd quality.

48.000 hertz Pro video, Dat audio, sampling rate of a lot of professional audio gear.

88.200 hertz Not often used doubling of the cd-quality, can sometimes be found.

96.000 hertz DVD audio quality supporting stereo-mixes up 5.1-surround-mixes.

192.000 hertz DVD audio quality supporting stereo-mixes.

ReferencesMcGuire, Sam, and Roy Pritts. Audio Sampling: A Practical Guide. Burlington, MA: Focal Press, 2008.

Thompson, Daniel M. Understanding Audio: Getting the Most out of Your Project or Professional Recording Studio. Boston: Berklee Press, 2005.

Winer, Ethan. The Audio Expert: Everything You Need to Know about Audio. Waltham, MA: Focal Press, 2013.

Stanley, R Audio in Media 10th Edition. : Michael Rosenberg 2014

Audio Engineering Society (AES): www.aes.org

Audio Publishers Association (APA): www.audiopub.org

audio-tutorials/season-3-mixing/Episode-7-Digital-Audio-Sample-Rate-Bit-Depth.html

Referenceshttp://audio-converter-software-review.toptenreviews.com/why-convert-wma-to-mp3-.html

http://lifehacker.com/5927052/whats-the-difference-between-all-these-audio-formats-and-which-one-should-i-use

http://www.digitalpreservation.gov/formats/fdd/fdd000027.shtml

http://whatis.techtarget.com/fileformat/WMA-Audio-file-in-Microsoft-Windows-Media-format