You must write a lab report for sound and music module, I will post the lecture slides for that module so you can read it and go over it.
OPEM: Sounds and Musical Tones (v.2024) (20 marks) Name: ________________________________________ Date: ________________________________________ Student Number: _______________________________ Lab partner (if any): _____________________________ You are allowed to work with another student in the class as a lab partner. You can work together to build the rubber band guitar, help each other to record the spectrum. However, you can NOT share the same photo, spectrum, screen shots or data. Even you are sharing the same rubber band guitar, or the same person is making the vocal sound, the data must be recorded separately. Adjust the rubber bands and the pitch of your voices so the frequency spectrum will be different between your data. Photo of the rubber band guitar (1 mark) Please insert a photo of your rubber band guitar. Add text of your name somewhere around the center of the photo. Part 1 Simple Tone Spectrum: Graphs. ___________________________________________________________________________________________ Please insert the screen shots of spectrum analyzer plot for with and without 1000 Hz test tone. Add text of your name somewhere around the center of the screen shot. (2 marks) Observation of Frequency of Single input Tone and Sound Level (SL) (2 marks, minimum of 6 tones required) Selected Tone Value (Hz) Measured Frequency (Hz) Measured SL (dB or dBFS) 1000 Graphs. ___________________________________________________________________________________________ (Insert Graph of Measured SL (in dB or dBFS) vs Selected Tone Frequency) (1 mark) Make sure to give a Title to your graph, label your axes, and insert units. Part 2: Rubber band Guitar: Insert a screen shot of the spectrum of one of your rubber band guitars. Add text of your name at the center of the screen shot. Study of Rubber Band Guitar Fundamental Tones and Harmonics (3 marks) Frequency Peak #1 Frequency Peak #2 Frequency Peak #3 Frequency Peak #4 Frequency f () SL (dB) Frequency f () SL (dB) Frequency f () SL (dB) Frequency f () SL (dB) Rubber Band #1 Rubber Band #2 Rubber Band #3 Graphs. ___________________________________________________________________________________________ Insert Graph of measured frequency of the peaks (y-axis) vs their Harmonic order (x-axis) for one of your selected rubber band vibrations Make sure to give a Title to your graph, label your axes, and insert units, if needed) trendline is welcome but not required (1 marks) Part 3: Human vocal cords Record the spectrum of a long “woooo…” sound made by human vocal cords at 3 different pitches. Insert a screen shot of one of the spectrum below (Add text of your name somewhere around the center of the screen shot) (insert screen shot here) Study of vocal cords Fundamental Tones and Harmonics (3 marks) Frequency Peak #1 Frequency Peak #2 Frequency Peak #3 Frequency Peak #4 Frequency f () SL (dB) Frequency f () SL (dB) Frequency f () SL (dB) Frequency f () SL (dB) Vocal pitch #1 Pitch #2 Pitch #3 Graphs. ___________________________________________________________________________________________ Insert Graph of measured frequency of the peaks (y-axis) vs their Harmonic order (x-axis) of the vocal voice. Make sure to give a Title to your graph, label your axes, and insert units, if needed) trendline is welcome but not required (1 mark) Answer the following questions. Explain your arguments. Summary of Questions: (6 marks) 1. In your study of the pure tones. Did you notice that for some sounds, the tones seemed extremely loud while others sound quite hard to hear? Does the spectrum analyzer SL results agree with your perceived level of loudness? Explain. 2. Based on your results plotting the Sound Level versus the Test Tone Frequencies: What role does your hearing response play? What role does the speaker or microphone response play? Try playing the files through headphones. Do you hear a greater range of tones? If you put the device with the Spectrum analyzer application near the headphone, does it have the same relative SL at all frequencies? Explain what you think is the explanation. 3. In your study of the rubber band guitar: If you look at the intensities of each frequency peak for a particular rubber band, is the fundamental the strongest? By changing the tension on the elastic band what happens to the frequency of vibration of the peaks? Explain why you think this happens. 4. When you plucked the elastic band between your fingers, was the sound as loud as what you got when you stretched it across the box? The elastic band’s vibration do not move the air very efficiently by directly pushing the air but when the band is attached to the box, the vibrations from the band vibrate the box and the box becomes like a loud speaker coupling its vibrations to the air and making a louder sound wave. Give some examples of musical instruments that use this principle. Electric guitars do not need a sound box since a detector senses the string vibration electrically below the vibrating wire and amplified using circuitry. 5. The generally accepted standard range of audible frequencies for humans is 20 to 20,000 Hz. Let us imagine that a particular musical instrument produces at sound with a fundamental note C8 at f = 4186 Hz and harmonics. If the instrument generates many harmonic orders, how many harmonics (including the fundamental) of this note will a human being be able to detect? List all the frequencies. 6. You may notice that when you are near an electrical transformer station, you hear a low frequency hum coming from the transformers. This is due to the 60 Hz AC electric current flowing the coils and around the core of the transformer. However, it turns out that the actual main frequency of the sound heard by the human ear is at 120 Hz. Using your knowledge of fundamental and harmonic overtones, present a possible explanation for this effect. 1 1 Sounds and Musical Tones(v.2024) Purpose: In this laboratory, you will use an installed application on your cell phone or tablet to analyse the frequency content of sound and musical tones while exploring concepts such as frequency, wavelength, and sound level. You will also see that musical tones and sounds may be composed of super-positions of more than one frequency element or component. We also see how some sounds are made up of fundamental and harmonic components. Apparatus: 1). Cell phone or Tablet capable of running Spectrum analyser software, 2). MP3 player or device capable of playing downloadable sound files (PC, Laptop, personal MP3 player etc…), 3). Plastic food storage box, 4). Rubber bands of different thicknesses, 5). Adhesive tape. Background: Musical Notes and the Musical scale: Figure 1: example of a sinusoidal pressure wave creating a pure tone and arriving at our ear for sensation. Creative commons CC0 , 1.0 2 When the sound waves are repetitive, and if the pressure wave follows a sinusoidal pattern, you hear a note or tone with a pitch equal to the frequency of the wave. Most music is composed around the intervals that are the frequency ratio between two different tones. The most important interval in music is the octave where the frequency ratio between the two tones is 2 to 1. The frequency of a pure sine wave sound wave is the basis for the musical notes developed for the writing and playing music. Western music is constructed around a note called A4, which has a standard pitch (Frequency) of 440 Hz. At intervals of approximately 9/8, 5/4, 4/3, 3/2, 5/3, and 15/8 above A4 lie the notes that make following steps in the scale. The next octave starts at a frequency twice that of A4 at 880 Hz which is the note A5. Table 1 on the following page shows the frequencies of the fundamental tones of the notes of music together with the wavelength the sound wave would have under conditions of air pressure at sea level and room temperature. In practice, western music is constructed over a span of 12 notes and 11 intervals that lie within the single octave (see Table 1). This allows the composer the work within major and minor keys and add sharp (#) or flat (b) notes from the main scale as needed. The pure tones that you hear from a tuning fork or an electronic oscillator frequently are not quite what is heard from musical instruments. Most instruments will produce a sound at the main note or fundamental frequency and will create sound waves that are integer multiples of the fundamental pitch (frequency). These are called higher- order harmonics. Take for example a violin, vibrating at fundamental note A4 (f=440 Hz). The string can also vibrate at the higher order harmonics of 880 Hz (2f), 1320Hz (3f), 1760 Hz (4f) etc…, i.e. the harmonic frequencies are equally spaced: 440Hz apart. Usually the fundamental frequency is the strongest with the higher order modes giving a small contribution. The violin’s sound is then a complex and subtle mixture of all these tones, which is known as the timbre of the instrument. The individual wave set up at the different frequencies all add up on the vibrating sting by a process known as superposition. They all exist together with almost no effect on one another and a rich and varied sound is created. Different instruments use different physical principles to generate their sounds but each has their own unique timbre that be recognized by the range of notes they can play and the harmonic content they have. Other aspects of sound generation tailor the sound but we will not touch upon this in this lab. NOTE C4 C#4/DB4 D4 D#4/EB4 E4 F4 F#4/GB4 G4 G#4/AB4 A4 A#4/BB4 B4 C5 C#5/DB5 D5 D#5/EB5 E5 F5 F#5/GB5 G5 G#5/AB5 A5 A#5/BB5 B5 C6 C#6/DB6 Frequency (Hz) 261.63 277.18 293.66 311.13 329.63 349.23 369.99 392.00 415.30 440.00 466.16 493.88 523.25 554.37 587.33 622.25 659.25 698.46 739.99 783.99 830.61 880.00 932.33 987.77 1046.50 1108.73 WAVELENGTH (CM) 131.87 124.47 117.48 110.89 104.66 98.79 93.24 88.01 83.07 78.41 74.01 69.85 65.93 62.23 58.74 55.44 52.33 49.39 46.62 44.01 41.54 39.20 37.00 34.93 32.97 31.12 Table 1: Partial List of Musical Notes of part of the Western musical scale together the Frequency and Wavelength of these tones under room temperature conditions near sea level. Table 1: List of Musical Notes of part of the Western musical scale together the Frequency and Wavelength of these tones under room temperature conditions near sea level. 3 Experiment: To perform the experiment, you will need to download an application to your cell phone, tablet or remote device that has a built in microphone. For Apple® based product go to the App store and download the application “Spectrum View” by Oxfordwave Research Ltd. For devices using the Android® system, you can try the application “Spectroid” by Carl Reinke, or “Spectrum Analyser” by Raspberry Wood located on the Google play store. Follow the installation instructions and learn how to modify the settings of the analyser using the help information included with the application. Your device should then be able to display the frequency content of whatever sound is entering the microphone. Turn off any gain limit that the device may have (see settings of application). To begin, you may want to reduce the sample rate of the application so that the spectrum analyser will show only the lowest frequency portion of the audio spectrum between 0 Hz and 4000 Hz. There are quite a few choices for display in these applications but we are interested in the “Spectrum Analyser” display. What you should see: The screen should show a graph of the current sounds observed. The horizontal or “x-axis” of the graph is the sound frequency in Hertz (Hz) while the y-axis plots the Sound Level (SL) given in decibels (dB). See figure 1 on the next page. Part 1 Simple Tone Spectrum: In this first step of the experiment, we will input a pure “sine-wave” tone into your device through its microphone by playing a sound. If you have a tuning fork at home