what the deuce is this?!?

hachi kid · #1 03-12-2010, 05:40 PM

http://www.vimeo.com/groups/inspire/videos/4041788

can someone explain what is happening here?.....

elgecko · #2 03-12-2010, 05:44 PM

Freaky! You get a similar effect by watching your strings with the TV in the background.

i_got_a_mohawk · #3 03-12-2010, 05:49 PM

Both effects are caused by the frequency of the electronic device (camera or TV) in relation to the frequency of the bass strings.

wabbit · #4 03-12-2010, 06:11 PM

sure i can 'try' to explain it

what you are seeing is slightly slowed down (and 'strobe' of the camera's shutter) footage of what a bass string, or any plucked/hammered string does .. you can obviously see on your own axe how the string vibrates when plucked but what you see in the video is what it actually vibrates/looks like

musical notes are at a particular frequency and depending on where your fretting finger is on the neck, determines the frequency that the string will vibrate at

for example, your low A is at a frequency of 440 Hz or 440 cycles/waves per second .. if you see the strings in the video as they are plucked, you will see a bunch of these 'waves' going up and down the string from his left hand finger to the bridge and back .. the frequency of these waves are what is interpreted by the pickups as the waves pass through the magnetic field .. this string/wave vibration within the magnetic field generates a signal that is passed to your amp and makes your speaker vibrate at 440 Hz which the human ear then interprets as an A note .. in an upright bass without pickups, the waves pass through the bridge into the air cavity inside the bass and the vibrating air escapes out the f holes to our ears

did that help?

**john turner** · #5 03-12-2010, 06:26 PM

Quote:

Originally Posted by i_got_a_mohawk

Both effects are caused by the frequency of the electronic device (camera or TV) in relation to the frequency of the bass strings.

yeah, it's called aliasing. it happens when the "sampling" frequency is less than 2x the highest "movement" frequency of the object being sampled.

it's why helecopter blades on tv shows seem like they arent moving, or are moving backwards, and wheels on moving cars.

nyquist theorem ftw!

**john turner** · #6 03-12-2010, 06:28 PM

Quote:

Originally Posted by wabbit

what you are seeing is slightly slowed down (and 'strobe' of the camera's shutter) footage of what a bass string, or any plucked/hammered string does .. you can obviously see on your own axe how the string vibrates when plucked but what you see in the video is what it actually vibrates/looks like

not precisely. you are seeing primarily the component of the vibrating string that is at a frequency multiple of the camera shutter speed. elements of the signal that are not even multiples of the camera shutter speed are what cause the string to look wobbly and mishappen.

FL Knifemaker · #7 03-12-2010, 06:31 PM

Quote:

Originally Posted by john turner

yeah, it's called aliasing. and wheels on moving cars.

nyquist theorem ftw!

In my hood we have wheels that do that without yo nyquist theorem

i_got_a_mohawk · #8 03-12-2010, 06:40 PM

Aliasing, that's the term I was looking for (friday night, long week

)

wabbit · #9 03-12-2010, 06:40 PM

Quote:

Originally Posted by john turner

not precisely. you are seeing primarily the component of the vibrating string that is at a frequency multiple of the camera shutter speed. elements of the signal that are not even multiples of the camera shutter speed are what cause the string to look wobbly and mishappen.

thanks for the clarification JT .. it's been awhile since i took this in school