Question

****Course is Technologies, Infrastructure and Architecture****

2. You are listening to your favorite music on bluetooth-radio-connected, non-mp3-player-containing, in-ear headphones, connected to your smartphone. The music is stored as an mp3 file that you downloaded from an online music store. Explain the process at a high level, end-to-end, using vocabulary from the reading in this course. 2.1 What major steps do you suppose were needed to convert the original performance's sound waves to mp3? 2.2 How is the mp3 transferred from the store to your smartphone? 2.3 How does an mp3 file on your smartphone become "music to your ears"? Your reply should be <400 words but use, accurately, at least these 12 terms: that include: analog, digital, signal, noise, A-to-D conversion, sampling, resolution (or bit depth), D-to-A conversion, carrier signal, modulation signal, volume (of data), velocity (of data). Tell the story at the level covered in the lecture, readings, and links of the past several weeks.

Answer 1

The constraints mentioned are applied for all the answers

Q.1 What major steps to produce were needed to convert the original performance's sound to mp3?

Air disturbances are what we interpret as sound is recorded. It can also be called as an analog signal. In order to actually play it on a device, the analog signal must be converted to a digital signal i.e. in 0/1 format. A device like microphone is used to pick up the analog signal, but before the microphone itself there is a filter which is responsible for filtering out the noise. The analog signals are represented as voltage levels which is then passed on to an Analog to Digital converter. Before the actual conversion itself the signals are modulated that is a signal is represented with another signal by changing a property. The signal that carries the signal is carrier signal and here it is the recorded audio and the modulation signal itself is another analog signal. The signal itself is sampled that is a rate is specified at which the quality or resolution in terms of bits per second of audio is decided. Although one thing to note higher the quality, higher the volume of data that is size. Finally the data is converted in bits (0 and 1) and that is stored as a file with .mp3 format. The file itself is stored on a central server that other devices can connect to actually get the file . The data encoded in this form can be used by speakers that have digital to analog converter to play the audio.

Q.2 How is the MP3 transferred from the store to your smartphone?

As said above the analog signal is stored in digital format as .mp3. This file is stored in a server that we refer to as a store. This server can accept connection from multiple devices simultaneously. One such device is your smartphone. Your smartphone connects to the store i.e. server. The user can select which .mp3 file i.e. which song dl you wish to have. Once selected we can select the resolution/quality of song in terms of bits per second. Interestingly, even when transferring data that signal itself is also modulated to be able to transfer. The quality you choose affects the size and is dependent on your internet speed. This digital file can be played on speakers/headphones by the aid of a digital to analog converter. The signal can then be sampled at high velocity to be able to hear.

Q.3 How does an mp3 file on your smartphone become "music to your ears"?

The file .mp3 contains the necessary data to reconstruct the analog signal to be able to play. The data is in a digital form. The way it plays is when you click on your favourite song in your music player, the file is sampled at high velocity and is converted to analog form by digital to analog converter and the time it takes is directly related to the resolution of audio. Once the data is converted in analog form it is then transmitted to the either the speaker/headphones via a 3.5 mm jack or Bluetooth signals. Once the signals reach the actual device it is then modulated to be able to drive the drivers whose movements are responsible for converting the voltage to air disturbances which our ears interpret as music.