Chapter 5 Sound Prepared by: Ms. Ma. Anna Corina G. Kagaoan College of Arts and Sciences

Objectives: Learn how to use sound in a multimedia project; Learn how to use MIDI and understand its attributes, especially relative to digitized audio; Learn to calculate sampling sizes and considerations for digitized sound; Record, process, and edit digital audio; and Determine which audio file formats are best used in multimedia projects.

Sound Perhaps the most sensuous element of multimedia. Meaningful “speech” in any language, from a whisper to a scream. Can provide the listening pleasure of music, the startling accent of special effects, or the ambience of a mood-setting background. Some feel-good music powerfully fills the heart, generating emotions of love or otherwise elevating listeners closer to heaven. How the power of sound is used can make the difference between and ordinary multimedia presentation and professionally spectacular one. Misuse of sound, however, can wreck your project.

The Power of Sound Acoustics – the branch of physics that studies sound. Decibels (dB) – measure of sound pressure levels (loudness or volume). The ratio between a chosen reference point on a logarithmic scale and the level that is actually experienced. Sound is energy. Too much volume can permanently damage the delicate receiving mechanism behind your eardrums. What you hear subjectively is not what you hear objectively. The perception of loudness is dependent upon the frequency or pitch of the sound. You may feel the sound more than hear it.

Multimedia System Sounds WAV files – system sounds in Windows, they reside in the Windows\Media subdirectory. Examples: start.wav, chimes.wav, ding.wav, logoff.wav, notify.wav, recycle.wav, tada.wav and Microsoft sound.wav. You can assign these sounds in system events such as Windows startup, warnings, clicks, etc. AIF format – system sounds in OS X on Macintosh. You can only change the system alert sound in this platform. Custom sound files may be put into ~/Library/Sounds. Digitally recorded audio or MIDI (Musical Instrument Digital Interface) – most sound used in multimedia productions.

Digital Audio Created when sound wave is represented using numbers—digitizing. Digitized sound is sampled sound. Every nth fraction of a second, a sample of sound is taken and stored as digital information in bits and bytes. Sampling rate or frequency – how often the samples are taken. Measured in kilohertz, or thousands of samples per second. Bitdepth, sample size, resolution, or dynamic range – how many numbers are used to represent the value of each sample.

Digital Audio Device independent – quality of audio is based on the quality of recording and not the device on which it will be played. CD-quality: 44.1 kHz, kHz, and kHz – three sampling frequencies most often used in multimedia. Quantization – rounding off to the nearest integer the value of each sample. If the amplitude is greater than the intervals available, clipping of the top and bottom of the wave occurs. Can produce an unwanted background hissing noise, and clipping may severely distort the sound.

Preparing Digital Audio Files Fairly straightforward, analog source materials—music or sound effects recorded on analog media such as cassette tapes—could be digitized by recording onto computer-readable digital media by playing sound from one device right into your PC using digitizing software. Focus on two crucial aspects: Balancing the need for sound quality against file size. Higher quality means larger files, requiring longer download times on the Internet and more storage space on a CD or DVD. Setting proper recording levels to get a good, clean recording.

Preparing Digital Audio Files File Size Versus Quality Sampling at higher rates (44.1 kHz or kHz) more accurately captures the high-frequency content of sound. Audio resolution (8- or 16-bit) determines the accuracy with which a sound can be digitized. More bits yields a recording that sounds more like its original. Stereo recordings are more lifelike and realistic than mono recordings. Formulas for determining size: Monophonic recording: sampling rate * duration of recording in seconds * (bit resolution/8) * 1. Stereo recording: sampling rate * duration of recording in seconds * (bit resolution/8) * 2. (Sampling rate (in kHz)* 1000)

Preparing Digital Audio Files Setting Proper Recording Levels Digital audio recording and editing software will display digital meters to let you know how loud your sound is. Unlike analog meter that usually have a 0 setting somewhere in the middle and extend up into ranges like +5, +8, or even higher, digital meters peak out. To avoid distorting, do not cross over limits where the digital meter peaks out. Keep peak levels between -3 and -10.

Preparing Digital Audio Files Editing Digital Recordings Audacity is a free open source editing application for Windows, Macintosh, and Linux operating systems ( Multiple Tracks – being able to edit and combine multiple tracks (for sound effects, voice-overs, music, etc.) and then merge the tracks and export them into a “final mix” to a single audio file. Trimming – removing “dead air” or blank space from the font of a recording and any unnecessary extra time off the end. Accomplished by dragging the mouse cursor over a graphic representation of your recording and choosing a menu command such as Cut, Clear, Erase or Silence.

Preparing Digital Audio Files Editing Digital Recordings Splicing and Assembly – removing the extraneous noises that inevitably creep into a recording. Cutting and pasting together many shorter ones. Volume Adjustments – providing a consistent volume level for multiple recordings. Use a sound editor to normalize the assembled audio file to a particular level, 80 percent to 90 percent of maximum. Format Conversion – reading a format different from that read by presentation or authoring program. Resampling or Downsampling – reducing the number of samples. Saves disk space Fade-ins and Fade-outs – enveloping capacity for long sections. Helps to smooth very beginning and very end of a sound file.

Preparing Digital Audio Files Editing Digital Recordings Equalization – modifying a recording’s frequency content so that it sounds brighter or darker also called digital equalization (EQ). Time Stretching – altering the length of a sound file without changing its pitch. Digital Signal Processing (DSP) – processing the signal with reverberation, multitap delay, chorus, flange, and other special effects. Do not overdo the sound effects. Reversing Sound – reversing all or a portion of a digital audio recording. Can produce a surreal, otherworldly effect when played backward.

Making MIDI Audio Takes time and musical skill to work with MIDI (Musical Instrument Digital Interface). You will need the following: Sequencer software – lets you record and edit MIDI data. Sound synthesizer – typically built into the sound board on PCs, but an add-on board for Macintosh). MIDI keyboard – useful for simplifying the creation of musical scores. Can easily edit score. Device dependent – quality of the playback depends upon the end user’s MIDI device. General MIDI numbering system – identifies instruments that can be synthesized. A production tool rather than a delivery medium. The best way to create original music.

Audio File Formats A recognized methodology for organizing the digitized sound’s data bits and bytes into data file. Linear Pulse Code Modulation – storage method used for Red Book Audio data files on consumer-grade music CDs. CD can provide up to 80 minutes of playing time, enough for a slow-tempo rendition of Beethoven’s Ninth Symphony. Incidentally, being able to contain Beethoven’s Ninth is reported to have been Philip’s and Sony’s actual size criterion during early research and development for determining the sectors and ultimately the physical size of the compact disc format itself. CD-ROM/XA (extended architecture) – format for reading and writing CDs developed to put several recording sessions onto a single CD-R disc.

MIDI Versus Digital Audio MIDI (Musical Instrument Digital Interface): Communications standard developed in the early 1980s for electronic musical instruments and computers. Allows music and sound synthesizers from different manufacturers to communicate with each other through cables connected to the device. Provides a protocol for passing detailed descriptions of a musical score, such as the notes, sequences of notes, and the instrument that will play these notes. Not digitized sound, it is a shorthand representation of music stored in numeric form. A score dependent on the quality of your musical instruments and the capabilities of your sound system.

MIDI Versus Digital Audio Digital Audio: A recording that depends only on the capability of the sound system. The actual representation of a sound, stored in the form of thousands of individual numbers. The digital data represents the instantaneous amplitude of a sound at discrete slices of time. Not device dependent so it sounds the same every time it is played. Large data storage files. Used for music CDs and MP3 files.

Advantages of MIDI Much more compact and the size is completely independent of playback quality. Files embedded in web pages load and play quicker. If the MIDI sound source is of high quality, they may sound better than digital audio files. You can change the length of a MIDI file (by varying its tempo) without changing the pitch of the music or degrading the audio quality. Completely editable—right down to the level of an individual note. The smallest detail of a MIDI composition can be manipulated.

Disadvantages of MIDI Because MIDI data does not represent sound but musical instruments, playback will be accurate only if the MIDI playback device is identical to the device used for production. Cannot easily be used to play back spoken dialog, although expensive and technically tricky digital samplers are available.

Advantages of Digital Audio Consistent playback quality. There is increased confidence that the audio track for the multimedia project will sound as good in the end as it did in the beginning when it was created. A wider selection of application software and system support is available for both Macintosh and Windows platforms. Preparation and programming required for creating do not demand knowledge of music theory.

Choosing Between MIDI and Digital Audio In general, use MIDI data when: Digital audio won’t work because you don’t have enough RAM, hard disk space, CPU processing power, or bandwidth; You have a high-quality MIDI sound source; You have complete control over the machines on which your program will be delivered, so you know that your users will have high-quality MIDI playback hardware; and You don’t need spoken dialog.

Choosing Between MIDI and Digital Audio In general, use digital audio when: You don’t have control over the playback hardware; You have the computing resources and bandwidth to handle digital files; and You need spoken dialog.

Sound for the World Wide Web 2 methods for playing digital or MIDI sound on the Web: (1) wait for the entire sound file to download to your computer, then play it back with a helper application; and (2) begin to play the sound file being downloaded as soon as enough of the sound is cached in your computer’s buffer (a place where data is stored temporarily). Streaming files is dependent upon connection speed: you must wait longer (streaming latency) before the streamed sound begins to play for slower connections.

Adding Sound to Your Multimedia Steps to bring an audio recording into your multimedia project: 1.Determining the file formats that are compatible with your multimedia authoring software and the delivery medium(s) you will be using. 2.Determine the sound playback capabilities (codecs and plug-ins) that the end user’s system offers. 3.Decide what kind of sound is needed (such as background music, special sound effects, and spoken dialog). Decide where these audio events will occur in the flow of your project. Fit the sound cues into your storyboard, or make up a cue sheet.

Adding Sound to Your Multimedia Steps (continued)… 4.Decide where and when you want to use either digital audio or MIDI data. 5.Acquire source material by creating it from scratch or purchasing it. 6.Edit the sounds to fit your project. 7.Test the sounds to be sure they are timed properly with the project’s images. This may involve repeating steps 1 through 4 until everything is in sync.

Music CDs ISO or Red Book (derived from the standard’s book jacket) – international standard which is the method for digitally encoding the high- quality stereo of the consumer CD music market. Developers of this standard claim that the digital audio sample size and sampling rate of Red Book Audio (16 bits at 44.1 kHz) allow accurate reproduction of all sounds that humans can hear.

Copyright Issues Ownership rights are significant issues for multimedia producers and play it safe by making their own music from scratch in a sound studio or with synthesizers. You can purchase and use digitized clip sounds with an unlimited-use, royalty-free license.

Time for Questions ? ? ? ? ? ?

Thanks … References: Books: Multimedia: Making It Work By: Tay Vaughan Web sites: