BADP2003 Light + Sound ASSIGNMENT 1

AIMS

The aims of this assignment are to:

.    develop further understanding of physical quantities and units essential to working with light and sound;

.    develop experience-based appreciation of the meaning of quantities in light and sound;

.     build ability and confidence to do simple calculations of the behaviour of light and sound in the environment; and

.    get you to start thinking about light and sound, to help you develop better ideas in the other two assignments.

PRAGMATICS

The data collection parts of the assignment is done by group work in the tutorials (weeks 1-4). There are probably 3-4 people in each data collection group. The calculation tutorial covers key calculation techniques relevant to the assignment, and lectures 1-3 should be particularly helpful.

The analysis and writing of the assignment is done individually, and the assignment is submitted individually.

This assignment contributes to 25% of your overall mark for Light and Sound.

Submit your assignment as a PDF document via Canvas.

DO NOT INCLUDE YOUR NAME IN THE ASSIGNMENT OR IN THE FILE NAME. University policy requires anonymous marking of written submissions where possible.

To ensure you assignment is correctly marked, please include headings for each part according to the headings below (Part 1. Acoustics, Part 2. Lighting, Part 3 Reflection) in your pdf, as each section may be marked by different tutors with expertise in these fields.

ACOUSTICS PART

For this part of the assignment you will analyse and discuss your measurements from the sound measurement tutorial. This part is worth 35% of the mark for this assignment.

BACKGROUND NOISE ANALYSIS

Describe and discuss your background noise measurements (up to 150 words), including the following [10%]:

.     Report the various background noise measurements that you made, and calculate the averaged sound pressure level of the background noise (i.e. overall LAeq).

.    Compare the background noise sound pressure level to recommended values for this type of room (you will need to find this information and cite it).

.    What were the main sources of background noise? Very briefly describe their signal characteristics (consider: loudness, spectral balance, fluctuation and tonalness, as discussed in the lecture).

PHONE-SOUND SOUND PRESSURE LEVEL MEASUREMENT ANALYSIS

Describe, analyse and discuss your phone-sound measurements (up to 150 words), focussing on the spatial decay rate (is the inverse square law evident?), as indicated below [15%]:

.     Provide a quick sketch of your measurement set-up, showing the position of the phone, the table,

the sound level meter positions, and the major nearby surfaces (walls, furniture, people if relevant).

.    Create a plot showing the measured sound pressure level as a function of distance from the phone, for the three repeated measurements (data from Step 6 of the tutorial), together with the average  result of the three (using the decibel arithmetic methods described in the lectures and sound calculation tutorial and lecture). You should use a logarithmic scale for distance (so that if the inverse square law is evident, it is expressed as a straight line). Also plot the background noise sound pressure level (assume that it is the same at all distances, preferably using the overall LAeq).

.     Repeat the above, but for the data in Step 7 of the tutorial.

.    Considering that your measurements of the phone may be noise-affected, try to subtract the

background noise from the data in Step 6. Note that there may be some problems with this when the phone’s sound (which includes background noise) is close to (or equal to, or less than) the separately measured background noise level.

Discuss the extent to which the results show evidence of the inverse square law. Please include quantities in your discussion, not just visual impressions of the plots. Consider reasons why there might be deviations from the inverse square law (your sketch of the set-up might help here). Does the inverse square law apply when the phone faces away from the measurement line (and why)? Does subtracting background noise help or introduce problems with your analysis? Using selected values from your Step 6 data, and assuming that the phone emits sound omnidirectionally (when not on a table), estimate the sound power level of the measured phone sound. [10%] (up to 150 words)

LIGHTING PART

For this part of the assignment you will analyse and discuss your results from the light measurement tutorial. This part is worth 35% of the mark for this assignment.

First, consider the parallel lamp orientation measurements (steps 4-8) you made in your tutorial. Use the illuminancelamp value for the 15 cm distance and the inverse square law to calculate luminous intensity.

Luminous intensity does not change with distance. With the calculated luminous intensity, use the inverse square law to calculate the expected illuminance at the other distances tested (20 cm, 25 cm, 30 cm, and 35 cm). Show your calculations, remembering to provide units. Compare your calculation results with your measurements. Provide a brief (up to 150 words) discussion on this comparison. Consider what the calculation results and measurements have in common. Speculate about possible reasons for any inconsistencies between them. [12 %]

Then, consider the perpendicular lamp orientation measurements (steps 9-10) you made in your tutorial. Since luminous intensity can change with lamp orientation, use the luminous intensity calculated for the parallel lamp orientation and Lambert’s cosine law to calculate the theoretical luminous intensity for the perpendicular lamp orientation. Separately, calculate the luminous intensity by using the illuminancelamp value for the 15 cm distance (perpendicular lamp orientation) and the inverse square law. For both sets of calculations, show your work and provide units. Compare the results of these two calculations. Provide a brief (up to 150 words) discussion on this comparison. [12 %]

Finally, using one of the luminous intensity values calculated for the perpendicular lamp orientation (you decide which one to use), use the inverse square law to calculate the expected illuminance at the other distances tested (20 cm, 25 cm, 30 cm, and 35 cm) for this orientation. Show your calculations and provide units. Compare your calculation results with your measurements. Provide a brief (up to 150 words) discussion. Consider whether the change in orientation made a difference to the relationship between distance and illuminance. [13 %] 

REFLECTIVE PART

This part of the assignment is to be done individually. It is worth 30% of the mark for this assignment.

In the first weeks of this unit of study we have considered many similarities and differences between light and sound.

Thinking about your experiences and results in the lighting and acoustics measurement tutorials, identify ways in which sound and light behave analogously, and/or ways in which they behave differently. You must  incorporate specific findings from your tutorial experiments in your discussion. You can also draw upon your everyday experience of light and sound, and on the theoretical material presented in lectures.  Your response to this part of the assignment does not need to be comprehensive, but instead should highlight three or four particular issues, discussing them clearly and insightfully.

Of course, external sources of information (if used) must be identified by in-text citations and references (we don’t mind which style you use, but if you want a suggestion try APA 7th  referencing style, https://apastyle.apa.org).

(up to 400 words, not including references)

[30%]

HOW TO DO WELL IN THIS ASSIGNMENT

The main aim of answering an assignment question is to show that you thoroughly understand the concepts and issues that it raises.  If you fail to show the required understanding, you will lose marks.

In numerical work, you show understanding by:

ü Correctly showing how a solution is calculated;

ü Giving the correct answer;

ü Using correct units;

ü Where relevant, providing insightful comments on the implications of the results; and

ü When creating plots, formatting them so that the relevant information can be seen easily, labelling them correctly, and interpreting the results correctly.

In work that involves theory and measurement, it can be useful to demonstrate an appropriate understanding of the limitations of each, which can be used to help understand discrepancies between them. Theories have assumptions, and measurements have sources of uncertainty.

In non-numerical work, you show understanding by

ü Correctly explaining the issues involved;

ü Answering in sufficient detail;

ü Reaching the correct conclusion; and

ü Drawing on relevant high quality external sources of information.

Sometimes illustrations are more effective than words in explaining concepts.

Read the question – make sure that you are answering what it is asking.

Justify your answers – either by derivation, or by explanation.

Try to explain things well – be succinct but not cursory, and use pictures if they help with explanations. Clear expression is highly valued in science: aim to write with maximum clarity.

Including irrelevant information may demonstrate a lack of understanding (especially if you argue that it is relevant).

Remember to answer every part of the assignment.

Be sure to adhere to the University’s academic integrity standards!!