Unit 2 Sound and Storage - Digitising Sound PDF

## **Unit 2: Sound and storage Lesson 1** ### **Digitising sound** **Related topics** - Creative use of computing. - Binary data **Key words** - Digital - Sample rate - Frequency - Stereo - Amplitude - Mono - Waveform - Analogue - Pitch - Bit depth **Learning objectives** 1. Understand the conc...

## **Unit 2: Sound and storage Lesson 1** ### **Digitising sound** **Related topics** - Creative use of computing. - Binary data **Key words** - Digital - Sample rate - Frequency - Stereo - Amplitude - Mono - Waveform - Analogue - Pitch - Bit depth **Learning objectives** 1. Understand the concept of digitised sound. 2. Understand the terms sample rate and bit depth. 3. Understand how digital audio can be represented using a visual waveform. ### **Digitised sound** Music, singing or conversation recorded by a microphone is an analogue recording. Examples of analogue audio include vinyl records, cassette tapes and magnetic tape systems. However, to be stored on a computer, an analogue recording needs to be converted into a digital format and stored like any other computer file, using binary. Examples of digital audio include: - mp3 and Waveform Audio File Format (WAV) files - DAB (Digital Audio Broadcasting) radio - podcasts and audio streaming services To convert an analogue sound to a digital sound, we use a method called sampling. Sampling records a digital version of the sound at regular time intervals throughout the recording. The shorter the intervals, the more accurate the recording. ### **Sample rate and bit depth** In Year 8, you learned how the quality of digital image files is defined by resolution and colour depth. In a similar way, the quality of digital audio files is defined by sample rate and bit depth. - **Sample rate:** the number of times the audio is measured and recorded per second. A higher sample rate creates a more accurate recording. - The standard sample rate for high-quality audio is 44,100 Hz. (Hz stands for hertz, which is the number of samples per second.) - **Bit depth:** the number of bits used to store each sample. The more bits that are used, the longer the binary sequence, increasing the quality. - The standard bit depth for high-quality audio is 16 bits. ### **Real-world examples** Audacity is an open-source audio editing program. Being open source means it is completely free to use and share. It allows multi-track editing, audio conversion and audio effects. Audacity works with audio files that have already been converted into a digital format. ### **A visual sound waveform** In Year 7, you looked at the structure of a sound wave and how it is converted from analogue to digital. The chart axes are as follows: - **x axis:** time passing in seconds (also known as the frequency) - **y axis:** amplitude or loudness of the sound. ### **Waveform examples** These waveform examples show how the pattern changes to show different types of sound. ### **Mono and stereo** We generally listen to music in stereo, which means the file contains two separate audio tracks or channels. Mono audio contains a single channel of audio. Stereo is higher quality, but it results in a bigger file size. ### **Real-world advice** When recording audio, remember that information can never be added back into an audio file so always record at the highest quality possible. The limitation will usually be file size: a higher-quality audio file requires more storage space. ### **Further investigation** - Investigate whether you have access to Audacity or a similar software package and if so, experiment with importing and recording a sound for editing. - Many people still use some examples of analogue audio. Discuss with your family and classmates. What examples do they still use and why do they enjoy them? - Investigate the ongoing discussion of whether analogue or digital audio sounds better. What do you think? ### **Success criteria** - I know what digitised sound is and why it is used. - I know what the terms sample rate and bit depth mean - I know what a basic waveform looks like - I know how a waveform changes to show different types of sound ## **Unit 2: Sound and storage Lesson 2 & 3** ### **Calculating audio file sizes** **Related topics** - Creative use of computing - Binary data **Key words** - Megabit (Mbit) - Bit depth - Channels - Compressed - MPEG Audio Layer-3 (mp3) - Sample rate - Uncompressed - Waveform Audio File Format (WAV) **Learning objectives** 1. Understand the difference between compressed and uncompressed audio files. 2. Understand how to calculate the file size of uncompressed audio. 3. Be able to calculate audio file sizes for a range of scenarios. 4. Know the advantages and disadvantages of compressed and uncompressed audio ### **Audio file types** Once we have some digitally recorded audio, it needs to be saved on a computer in an appropriate file type. You should know that image files can use compressed or uncompressed formats. Audio files can be saved in the same way. - **Uncompressed audio** is when the sound is saved exactly as it has been recorded. - **Compressed audio** is when algorithms are used to compress (reduce) the size of the file. In some cases, inaudible elements are removed. ### **Calculating an uncompressed audio file size ** In order to calculate the file size in bits, the following information is required: - The **sample rate** - The **bit depth** - The **number of channels:** either mono (one channel) or stereo (two channels) - The **length of the sound in seconds**. The equation to calculate audio file size is below: $File size = sample rate \times bit depth \times number of channels \times file length$ This is an example for a one-minute mono file with a standard sample rate and bit depth: $File size =44,100 \times 16 \times 1 \times 60 = 42,336,000 bits$ File size in bits is often a very large number. We can make it easier to manage by converting it into megabits (Mbit). 1,000,000 bits is equal to 1 Mbit. The calculated file size above is about 42 Mbit. ### **Real-world examples** Uncompressed audio, such as a WAV file, can require a lot of data storage. During the 1990s, the mp3 file format was created to compress and reduce the size of digital audio files, especially music. This led to mp3 files becoming the common standard for digital music, despite many users' concerns about losing audio quality. In 2001, the first Apple iPod was released, taking advantage of the popular mp3 file type. Users could now carry around thousands of tracks on one device, rather than needing multiple CDs. This functionality is now a standard part of every smartphone. ### **File size scenarios** Here are two examples of common audio recording. Note the difference in file size, despite the sample rate and bit depth being the same. **Example 1:** Low quality mono audio voice recording, such as a voicemail recording. - Sample rate: 44,100 - Bit depth: 16 - Number of channels: 1 - Length: 30 seconds - File size = 44,100 x 16 x 1 x 30 - File size = 21,168,000 bits (21 Mb) **Example 2:** High quality stereo pop music track, designed to be downloaded. - Sample rate: 44,100 - Bit depth: 16 - Number of channels: 2 - Length: 3 minutes (180 seconds) - File size = 44,100 x 16 x 2 x 180 - File size = 254,016,000 bits (254 Mb) ### **Comparing compressed and uncompressed audio** When choosing how to record and save audio, it is important to consider the advantages and disadvantages of each. | | Advantages | Disadvantages | |-----------|------------------------------------------------------|-----------------------------------------------------------------| | Compressed | - Smaller file size | - Once data is removed, it cannot be restored, losing quality | | | - Easier to upload and download | - Listeners are missing out on the original audio | | Uncompressed | - Original quality is preserved | - Requires more storage | | | - It can be compressed later if needed | - Takes longer to stream/download | | | - Ideal for archiving | | ### **Further investigation** - Investigate some other audio file types. - Think of two more audio scenarios and ask a friend to calculate the file size for each. - Convert the file sizes in bits to bytes. (Remember, there are 8 bits in a byte.) ### **Success criteria** - I know what digitised sound is and why it is used. - I know what the terms sample rate and bit depth mean. - I know what a basic waveform looks like. - I know how a waveform changes to show different types of sound. - I know the difference between compressed and uncompressed audio files. - I know how to calculate the size of an uncompressed audio file. - I know some of the advantages and disadvantages of compressed and uncompressed audio. ## **Unit 2: Sound and storage Lesson 4** ### **Storage devices and storage media** **Related topics** - Use of technology in society - Binary data **Key words** - DVD - Blu-ray™ - Magnetic media - CD - Optical - Solid-state storage device **Learning objectives** 1. Understand the purpose of storage devices and storage media. 2. Know the three most common types of storage technology. 3. Understand the difference between storage devices and storage media. ### **What is storage media?** Storage media are the components of a computer system that store data. Common examples include: - CDs, DVDs and Blu-ray discs - Magnetic hard disks - Magnetic tape (found in cassettes) - Portable flash drives - USB pens or sticks - Memory cards. You will have used some of these types of storage media yourself. ### **What is a storage device?** A storage device reads and writes data to and from storage media. Examples of common storage devices include: - **An internal hard drive:** an essential part of modern computers. - **A CD, DVD or Blu-ray drive:** used to listen to music, watch television and load games. - **An external hard drive:** used to transfer files between computers and locations. ### **What's the difference?** Remember that only storage media can store data. Storage devices just read and write that data. For example, a DVD is a type of storage medium inserted into a DVD drive (a storage device). Your computer's hard drive may have a magnetic hard disk (storage medium) that is read by the hard disk drive (storage device). ### **Real-world examples** - The first magnetic hard drive was created by IBM in 1956. - The first CD was co-developed by Sony and Phillips in 1982. - The first solid-state drive (SSD) was sold by IBM in 1991, as part of their ThinkPad computer. ### **Storage technology** There are three common forms of storage technology in use today: | Type | Description | Used in | |---|---|---| | Magnetic storage | Uses spinning magnetic discs that contain data. | Hard disk drives, floppy discs, cassette tapes. | | Optical storage | Uses a laser to read tiny patterns on the disc. | CDs, DVDs | | Solid-state storage | Stores data on memory chips | SSD hard drives, USB flash drives | ### **Typical storage capacities** The storage capacity of modern devices is increasing every year, but below are some typical current examples. These are just a guide and many will already improve on these capacities. - An internal magnetic hard drive: 2 terabytes (TB) and above. - A portable hard drive: 500 gigabytes (GB) to 4 TB. - Magnetic computer backup tape: 500 GB to 5 TB. - A DVD: 4, 7 or 9.4 GB. - A Blu-ray disc: either 25 or 50 GB. - A USB pen drive: 8 GB to 64 GB. - A solid-state hard drive: 500 GB to 4 TB ### **Real-world examples** Although originally designed to hold a 74-minute album of songs, the CD could alternatively be used to store around 700MB of data. It quickly became a fast and cheap way to sell physical copies of computer software to different users. ### **Further investigation** - Select two types of storage from this unit and investigate their current maximum capacity. - Investigate the history and the future of storage technology. ### **Success criteria** - I know the difference between storage media and storage devices. - I can describe examples of storage media and devices. - I can describe some of the common capacities of modern storage media and devices. ## **Unit 2: Sound and storage Lessons 5 & 6** ### **Storage devices and storage media characteristics** **Related topics** - The internet and the world wide web (WWW) - Use of technology in society **Key words** - Access speed - Cloud storage - Durability - Energy efficiency - Portability - Reliability - Rewritability **Learning objectives** 1. Know the key characteristics of storage devices and media. 2. Understand how these apply to common storage devices and media. ### **Defining storage device and media characteristics** When selecting data storage for any purpose, there is always more than one option. It is important to consider the following storage characteristics. These will help the user to choose an appropriate storage type. - **Maximum storage capacity:** how many GB or TB of data can it hold? - **Cost:** how expensive is it compared with other devices? - **Ease of use:** does it require additional technology or skills to use? - **Reliability/Durability:** can it be easily damaged? Is it robust? How long will it last? - **Energy efficiency:** how much energy does it use? - **Access speed:** how quickly can data be accessed or written to it? - **Portability:** how easy is it to move or carry around? - **Rewritability:** can data be removed and rewritten more than once? ### **Cloud storage** Cloud storage is simply accessing high-capacity data storage via the internet, rather than a locally installed device. Users will access the space via a website or app and can store documents and files in the same way as any local storage device. There are many paid for and free services, but access is limited to locations with internet access. ### **Real-world examples** Although this book focuses on computer-based systems, data storage is now common in many household devices, especially those with 'smart' technology. These devices will generally use SSD storage to save space and provide a longer lifespan. Devices might include: - Smart televisions and audio equipment - Games consoles and entertainment systems - Kitchen appliances with multiple programme options. ### **Storage characteristics of common devices and media** In the table below, we will briefly consider the four types of storage technology you have encountered and examine how they compare against the most common characteristics. | Type | Capacity | Cost | Ease of use | Reliability/Durability | Energy efficiency | Access speed | Rewritability | |---|---|---|---|---|---|---|---| | Optical storage | Limited to manufacturing standards | High cost | Requires an optical drive to access it - not all drives read all discs | Fairly durable but will fail if scratched | Drive requires some power but is fairly energy efficient | Slow compared to other devices | Some discs are rewritable, but not all | | Magnetic storage | High capacity | Low cost | Common to most desktop computers | Designed for long term use but mechanical parts mean it will fail at some point | Moving parts require power but local storage is fairly energy efficient | Fast data access | Designed for rewritability | | Solid-state storage | Medium capacity | High cost | Commonly used | No moving parts - mean increased durability | Highly energy efficient due to low power requirements | Fastest data access, due to lack of mechanical parts | Designed for rewritability | | Cloud storage | Unlimited, as it often combines multiple devices. Depends on provider; some free options | | Normally web-based, requires web skills | | | | | ### **Further investigation** - Investigate two different cloud storage products: one free and one paid for. How do they compare? ### **Success criteria** - I can describe common storage characteristics. - I know what cloud storage is. - I can compare some of the specific characteristics of storage devices. ## **Unit 2: Sound and storage Mid-unit assessment** **Typical 4-mark exam question** As a sound engineer, you are working with a music band to record their first song. Describe whether you would create a compressed or uncompressed audio recording. Give two advantages and two disadvantages of your choice. **Specimen 4-mark answer** The recording should be made using uncompressed audio. **Advantages:** - None of the original data is lost and the file could be compressed for other uses later. **Disadvantages:** - It creates larger file sizes so more storage is needed. - It also may not be suitable for music streaming services. ### **What good things can we see in this answer?** 1. Good word choices: file sizes, lost data, storage. 2. The correct choice is given, since uncompressed audio should be used in this situation. 3. The advantages and disadvantages are correct and relate to uncompressed audio. ### **Which parts of the answer could be better?** 1. The 'other uses' of compressed audio could be explained. 2. The second disadvantage does not explain why an uncompressed audio file may not be suitable for streaming. ### **How can we improve this answer?** 1. Give examples of 'other uses' of compressed audio, such as streaming, downloads or portable music players. 2. Provide a reason why uncompressed audio may not be suitable for music streaming services. ## **Unit 2: Sound and storage Lesson 7** ### **Portable storage** **Related topics** - Use of technology in society **Key words** - Drone - Global positioning satellite (GPS) - Portable - Remote **Learning objectives** 1. Understand the term portable storage. 2. Describe real-world uses of portable storage. 3. Understand advantages and disadvantages of portable media. 4. Be able to suggest an appropriate portable storage option for a given scenario. ### **What is portable storage?** Portable storage describes any device or media that can be easily transported from one location to another. Often this includes storage that can be used on the move. Portable storage allows people to: - Copy files from one computer to another without needing internet access. - Remote working, at home or away from an office. - Work on the move, for example, on a train or bus. ### **Examples of portable storage** Portable storage can be found in computer systems and personal devices. Examples include: - USB pens or sticks, used to transfer files - Portable hard drives, both magnetic and solid-state - Solid-state memory cards - Laptops, which contain storage in hard drives - Smartphones and tablets - Portable gaming devices - Global positioning satellite (GPS) devices, used for navigation - Digital cameras and drones - Portable music players. ### **Real-world examples** The smallest commonly used memory card is a microSD, which is 15mm x 11mm. However, manufacturers are already releasing 'nano' sized cards which are even smaller. Nano SIM cards for smartphones have been used since 2012 and are now the most common type of SIM. ### **Advantages and disadvantages of portable storage** | | Advantages | Disadvantages | |---------------|----------------------------------------------------------------------------------------------------------------------------|-----------------------------------------------------------------------------------------------------------------------------------------| | **Advantages **| - Many portable storage devices are pocket sized and easy to carry. | - Portable storage devices can be lost, potentially losing important information. | | | - Allow users to transfer documents and files without network or internet access. | - Portable devices often have limited capacity. | | | - Compatible with most computer devices. | - Some devices do not have sockets (ports) for connecting portable devices. | | | - Some portable storage devices include security options such as password protection or fingerprint access. | - High-capacity portable storage can be very expensive. | | | - Available in a wide range of capacity sizes | - Can be used to accidentally transfer computer viruses. | ### **Portable storage scenarios** Below are three real-world scenarios, alongside a suggestion for the most appropriate portable storage to use and why it is appropriate. | Scenario | Portable storage choice | Reason for choice | |---|---|---| | Taking copies of a presentation to a meeting to hand out to colleagues. | CD/DVD disc. | Discs are cheap to purchase and have a high enough capacity for most presentations. | | Adding additional storage to a remote camera drone | Solid-state memory card. | Small size and durable enough to handle lots of physical movement | | Copying a computer's entire hard drive to a new computer | Portable magnetic hard drive | Available in large storage capacity and, being magnetic, not as expensive as solid-state. | ### **Further investigation** - Look back at the examples of portable storage. Which ones have you used? Discuss them with your teacher and class. - Investigate real-world examples of security information being found on a USB drive left on a train or bus. - Create two more scenarios like those in the table and suggest the most appropriate portable storage device for each, giving your reasons. ### **Success criteria** - I know what portable storage is. - I can describe examples of portable storage. - I can describe some advantages and disadvantages of using portable storage. - I can suggest the most appropriate portable storage for a given scenario. ## **Unit 2: Sound and storage Lesson 8** ### **User storage requirements** **Related topics** - Use of technology in society - Technology in the workplace **Key words** - Backup - Differential - Incremental - Restore - User needs **Learning objectives** 1. Understand the importance of considering user needs when suggesting storage solutions. 2. Be able to describe examples of storage scenarios. 3. Understand the importance of backing up data. 4. Be able to suggest an appropriate storage device for a given scenario. ### **Considering user needs** When specifying the requirements for any computer system, the amount of storage is dependent on the user needs. Look again at the list of characteristics that you met earlier in this unit. They form part of the following elements that should be considered: - What is the purpose of the system? - What data is going to be stored? - How much data is going to be stored? - How often will it be accessed? - How quickly will data need to be accessed? - What budget does the user have? ### **Simple storage scenarios** The examples below describe how storage might be specified for a simple problem. | Scenario | Solution | |---|---| | A drone pilot is creating a new film of a local popular rock-climbing area and is concerned about running out of storage while on the move. | They could carry spare solid-state memory cards to use if the drone's internal storage becomes full. | | A web designer wants to keep a copy of all their projects at home in case they can't make it to the office. | They could use a portable magnetic drive which has a high capacity and can be transferred between two locations. | ### **Real-world examples** One example of a product changing to meet user needs is that of portable music players. - Early music players used magnetic tape (in cassettes) that would wear out over time. - Portable optical disc (CD) players were prone to 'jumping' as users moved, interrupting the sound. - Early magnetic hard drive music players also jumped as users moved. - SSD music players removed these problems and increased the capacity. ### **The importance of backing up data** Having electronic-only copies of important files and documents presents a serious problem: what happens if the storage device fails or the computer is destroyed in some way? This creates the need for backed-up data. - **A backup** is a copy of all important files and documents. This copy can be kept safe in another location in case any files need to be restored. - **For a backup** to be up to date, it often needs to be regularly redone. - **Many users** are now using cloud-based backup systems. This means that their files and documents are copied, via the internet, to a remote secure storage location. ### **Complex storage scenarios** Study the following scenarios, which are more complex and require multiple solutions. | Scenario | What to consider | Potential solution | |---|---|---| | A team within an office is working on group project reports in the same room. Each person has their own desktop computer. | - Desktop computers don't need to move. - Users in the office will want to share files. - Reports are text-based and don't require lots of storage. | - Magnetic hard drives in each desktop computer. - USB sticks for quickly transferring files between computers if required. - Cloud storage could store finished reports. | | A group of scientists around the world are working together on a medical project. They will need to work remotely most of the time. | - Users within the group will want to share data. - Users will need to work with portable devices. They may need to process large files. | - SSD within laptops or tablets would allow users to work on the move. - Group files could be shared via a paid cloud storage system. | ### **Types of backup ** When backing up data, there are three methods to consider: - **Full:** a complete copy of all relevant files and documents. - **Differential:** a copy of only the changed data following a full backup. - **Incremental:** regularly timed backups that only save any changed data since the previous backup was carried out. Most users would not need to carry out a full backup every time, since this would take a long time and only a few files may have changed since the last backup. ### **Further investigation** - Consider two simple and two complex storage scenarios of your own. What solutions would you suggest for them? - Investigate and compare some current backup systems. - Discuss with your class and teacher how often they back up important files and documents. ### **Success criteria** - I know why user needs are important when suggesting storage solutions. - I can describe examples of simple data storage solutions. - I can describe examples of more complex data storage solutions. - I know how important it is to back up data. ## **Unit 2: Sound and storage Lessons 9 & 10** ### **Storage needs of an organisation** **Related topics** - Use of technology in society - Technology in the workplace - Computer systems **Key words** - Recommendation - User - Collaborative - Organisation **Learning objectives** 1. Understand the key storage requirements for a given organisation. 2. Be able to recommend storage devices and media for an organisation's specific needs. ### **Organisation details** The computer and storage requirements for any organisation vary according to its needs. In this section, we will be considering a small training college, specialising in computer science and technology subjects. The college has the following needs: - Teachers and students require user access around the college. - Each classroom contains either computers, tablets or workshops. - The college office contains administration computers and stores all college data. - Teachers and students will want to work in collaboration on group projects. - Presentations can be given by connecting to a large screen in the main hall. - Teachers and students may be working remotely at times. - Regular backups need to be taken of all college files and documents. - Security cameras are placed around the college. ### **Key storage requirements** Now consider the details of the training college above and focus on the storage requirements, which include: - Classroom computers - Office computers - Central network storage - Backup system - Teacher laptops and portable storage. - Online collaborative working. This college has a lot of different requirements. We can suggest appropriate solutions to meet each need. ### **Real-world advice** When thinking about the storage requirements of an organisation, it is essential to consider not just the present but also the future. What might change over time? Think about these questions: Will there be more users using the system in the future? - Can data storage be easily upgraded or increased? - What lifespan will any chosen technology have? ### **Recommendations based on key requirements** The following recommendations could be made to meet the needs of the training college. | Storage requirement | Recommendation | Reason | |---|---|---| | Classroom computers | Magnetic hard drives | High capacity, low replacement cost, fixed position | | Office computers | Magnetic hard drives | High capacity, low replacement cost, fixed position | | Central network storage | Magnetic hard drives | High capacity, low replacement cost, easily available, fixed position | | Backup system | Portable SSD | Can be easily moved to a remote, secure location when not in use. | | Teacher laptops | Solid-state hard drives | Ability to work on the move without issues, smaller and lighter. | | Teacher portable storage | USB pen drives (solid-state) | Low cost, easy to transport able storage from any location. | | Group Working | Cloud-based storage | | | Security cameras | Solid-state memory cards | | ### **Real-world examples** Around the world, users are mixing storage technology using a combination of optical discs, SSD and magnetic hard drives. In the future it is expected that most devices will move to solid-state storage as it becomes smaller and cheaper to produce. Solid-state storage is already in many of the devices we use and it is likely that optical and magnetic devices will be used less and less. In the distant future, we may see biological or even atomic storage, arranging atoms into data sequences. ### **Further investigation** - Come up with a similar type of organisation and list its potential storage requirements. What solutions can you suggest? - Investigate how data storage technology might develop in the future. ### **Success criteria** - I can create a list of key storage requirements for an organisation. - I can recommend a storage solution for an organisation's key requirements.