Goal: Establish a clear understanding of how loudness can differ from amplitude.
Options: See the exercises in the Moylan text at the end of chapter 13. Complete the first exercise (13-1) and report your results, with your own analysis or complete the experiment below and report your results.
For this assignment you will need a program which can play pre-recorded or synthesized audio signals, at least one loudspeaker and an SPL meter. iPhone and Android SPL apps will work fine for this. If you are on campus you can checkout one of the SPL meters from the studio monitor. You will need approximately 30 minutes to perform the experiments once your equipment and software are configured.
Specific Tools (if using NYU studios):
Work in groups of 2 or 3 if using the studios
Studio Computer, Laptop or mobile computing device.
Synthesis software (android app, iphone app, laptop app) or audio playback software.
Powered speakers (the JBL eons work great, they are in the “tech closet”).
Power cables for the speaker, plus maybe an extension cord.
audio cables to connect the laptop to the speaker audio inputs.
It may take you a few tries to get the right cables, give your self a few minutes for this process.
Sound signals needed:
100Hz sine wave at -20dB (8 seconds)
250Hz sine wave at -20dB (8 seconds)
500Hz sine wave at -20dB (8 seconds)
1kHz sine wave at -20dB (8 seconds)
1kHz sine wave at -20dB on sustaining, or looped
2kHz sine wave at -20dB (8 seconds)
4kHz sine wave at -20dB (8 seconds)
6kHz sine wave at -20dB (8 seconds)
8kHz sine wave at -20dB (8 seconds)
pink noise signal at -20dB (8 seconds)
white noise signal at -20dB (8 seconds)
Play the 1kHz sine wave into the sound system and adjust the levels until you get an SPL reading between 70 and 75 dB SPL on the meter or metering app.
Experiments: Play each of the test signals. Then play the short 1kHz tone against each of the other test signals by alternating (1kHz signal, then another test signal). Note how each one sounds in terms of perceived volume or loudness. Check your SPL meter reading with each signal to see if the levels actually change at all due to the sound system you are using or the acoustics of the space you are using for this experiment. Finally consider adjusting the level of each of the test signals until is sounds as though its the same level as the 1kHz sine wave. If you do this, be sure to record the SPL readings for each of the different sounds.
Analysis: Discuss wow the sounds compared to the 1kHz sine wave. Were some sounds more or less pleasant than others? Plot any measurements as a bar-graph, line graph or chart.
Reports are due as blog posts online before our next meeting. Please put the links to your posts as comments at the bottom of this assignment.