A bit confused about degrate~ and Aliasing when decimation
Hey guys，I bought Electronic Music and Sound Design Vol 2 and just started to learn the first chaper，a Aliasing patch kind confuse me（see image below）：
The thing is，from my understanding，Aliasing happens when the sample target's Frequency is higher than half of the Sample Rate（which is called Nyquist Frequency）,so if i'm using a 5khz SR to sample a 5.5khz sine，it will alias.
But the patch here is only downsampled by 1/8，which is still like 5k above，and the target's Frequency is 500hz，sine wave so no high Frequency Content，my question is why still need to add anti - Aliasing filter after decimation eventhough the SampleRate is way higher than needed？（which is 1khz）
My guess is after downsampling，Max kind add all possible Frequencies to the new sound（which is all Frequencies that should be aliased relative to 500hz and 5khz SR），because it didn't know what sound it is before downsample？I really dont know。
Here is the patch：
Up UP,still thinking about it
I tried to lower degrated sample rate and as guessing more Aliasing appeared，but still dont know what happened exactly
you got the nyquist theorem right, but you ignored that you are doing far more here than working in 5.5khz: you are changing the original rate, and if you do that, the values of the samples will become incorrect (and then you can hear that at 0.99 already)
if you would generate a perfect cosine only at every 8th sample in 44 kHz, it would not happen.
Thanks！So I'm guessing although I used degrade~ to downsample this sine，max is still working under 44.1khz，which means after downsample，max kind add all possible results about 500hz that could aliasing in a range of 22.05hz，above my current sample rate（5khz），right？
gogo~am i right？
not sure if i am really able to explain it properly, but yes, after [degrade~] the signal is of course still 44 khz, so some kind of conversion happened.
you will not get the full picture either when using [poly~ mycosine down 8] i am afraid.
luckily, with broad spectrum material it works much better than with a pure tone.