Week 3: Focus of Activity

Week 2: Focus of Activity

Q1 - In a recording room an acoustic wave was measured to have a frequency of 1KHz. What would its wavelength in cm be?

0.333m or 33.3cm. This is according to the equation that Lambda is equal to the velocity over frequency. An acoustic wave would travel at 333m/s through air meaning that the velocity is 333 and the frequency from the question is 1000 Hz.

Q2 - If a violinist is tuning to concert pitch in the usual manner to a tuning fork what is the likely wavelength of the sound from the violinist if she is playing an A note along with sound from the pitch fork?

440 Hz is the frequency of Concert Pitch. The velocity of the wave through a steel tuning fork is 5,000 m/s. The wavelength in cm would be 1137 cm. This is once again according to the aforementioned formula.

Q3 - If an acoustic wave is traveling along a work bench has a wavelength of 3.33m what will its frequency be? Why do you suppose that is it easier for this type if wave to be travel through solid materials?

Frequency is equal to velocity over lambda. The velocity of the sound is once again 5000 m/s and the wavelength is stated as 3.33m. So the frequency of the wave would be around 1501 Hz. The wave travels faster through solid materials This is because the particles (atoms or molecules) in a solid material are touching each other and rather fixed together and as such they collide with each other faster as the sound wave moves through them.

Q4 - Sketch a sine wave accurately of amplitude 10, frequency 20Hz. Your sketch should show two complete cycles of wave. What is the duration of one cycle? What is the relationship between the frequency and the duration of one cycle?

The duration of one cycle is equal to the number of cycles over the frequency. As such if you have a higher frequency you will have a shorter duration for the cycle and as such the wavelength shortens.

Q5 - Research the topic “Standing Waves”. Write a detailed note explaining the term and give an example of this that occurs in real life. (Where possible draw diagrams and describe what represent)

Standing waves are waves that remain in a constant position and do not travel through the transmission medium. These waves can be found in the strings of a musical instrument. In a violin string when it is either bowed or plucked the string vibrates as a whole between a two nodes at either end and an anti-node in the middle.

Q6 - What is meant by terms constructive and destructive interference?

Constructive Interference is when two waves that have been added together have a resulting larger amplitude. When this wave is larger than both of the originals then you have constructive interference. 

Destructive Interference is when the sum of the two waves added is less than than either original wave. So much so that it can be zero. This occurs when one of the waves starts with a trough and the other starts with a crest.

Q7 - What aspect of an acoustic wave determines its loudness?

The amplitude of the wave determines the loudness. A larger amplitude means more energy and as such produces a larger sound.

Q8 - Why are decibels used in the measurement of relative loudness of acoustics waves?

The reason that decibel is widely used as the measurement of relative loudness is that human ears perceive sounds in logarithmic scale instead of linear scale. So that we can graph a huge range of values such as there is in terms of volume, loudness we use this logarithm.

Q9 - How long does it take a short 1KHz pulse of sound to travel 20m verses a 10Hz pulse?

The frequency of a sound wave has no affect on the time it takes to travel. So using the equation that time is equal to distance divided by velocity.
t = 20/333s
= 0.06s

Q10 - The speed of sound in water is roughly 1,500 m/s. It moves much faster in water as opposed to air because the particles in water are much closer together than in a gas.