If you are getting odd noise when you talk on a call, that is an upstream issue, if people say you are breaking up, choppy for example. If you hear breaking up of voices, or choppy, that is a downstream issue. Make sure you don't here any breaking of audio (up or down) when NO ONE else is using your bandwidth, that will define your baseline is ok. If you get bad quality when no one else is using your bandwidth, that means either your ISP is limiting something or you are sending and receiving a lot of bad data or modem maybe retrying to get good data.
You should have power between 10/-10, which is ok for most modems. For your make and modem of modem there should be a specification sheet on what is normal ranges, and your ISP should publish the same as well.
As for your ping returns say to www.google.com being both faster and slower, that could be from a number of scenarios. Need more data to know if that is an issue or not. Each route of a ping can vary greatly based on what others are doing at the time you do the ping test. Cable is a SHARED bus, so if others are streaming a lot, you would expect your pings to be slow, etc.
Do you have any view that shows the correctable and uncorrectable codeword errors? This is also a good metric for tracking issues.
Here is a snapshot of my cable modem...
Downstream Bonding Channel Value Channel ID 15 16 17 18 19 20 21 22 Frequency 663000000 Hz 669000000 Hz 675000000 Hz 681000000 Hz 687000000 Hz 693000000 Hz 699000000 Hz 705000000 Hz Signal to Noise Ratio 36 dB 36 dB 36 dB 36 dB 37 dB 36 dB 36 dB 36 dB Downstream Modulation QAM256 QAM256 QAM256 QAM256 QAM256 QAM256 QAM256 QAM256 Power Level The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading -9 dBmV -9 dBmV -9 dBmV -9 dBmV -9 dBmV -9 dBmV -10 dBmV -10 dBmV Upstream Bonding Channel Value Channel ID 17 20 19 18 Frequency 17800000 Hz 37000000 Hz 30600000 Hz 24200000 Hz Ranging Service ID 9281 9281 9281 9281 Symbol Rate 5.120 Msym/sec 5.120 Msym/sec 5.120 Msym/sec 5.120 Msym/sec Power Level 44 dBmV 47 dBmV 46 dBmV 45 dBmV Upstream Modulation  QPSK  16QAM  64QAM  QPSK  16QAM  64QAM  QPSK  16QAM  64QAM  QPSK  16QAM  64QAM Ranging Status Success Success Success Success Signal Stats (Codewords) Bonding Channel Value Channel ID 15 16 17 18 19 20 21 22 Total Unerrored Codewords 3782278605 3782294806 3782259374 3782317826 3782261177 3782258912 3782254714 3782258905 Total Correctable Codewords 8780 9058 10931 4134 687 3032 9960 4669 Total Uncorrectable Codewords 1661 2428 1458 1527 2111 1658 620 2687
Here is the datasheet for my modem...
Notice my downstream SNR is below 39, the higher the better is the general rule, but it varies based on the QAM settings, so I have good quality signals coming my AMP, and I have a signal filter on the AMP, so that helps keep the SNR up even though by cable modem is a long distance from my AMP and the ISP hub. But too high is also an issue, which most tutorials do not explain as an issue. But lets ignore that for now.
My upstream SNR is a bit off specification, but again, I have a long distance between point to point as noted above. As long as I am just gaming and surfing, I am not sending a lot of data back to the ISP compared to a business or such, so I am not flooding the up channels. Thus a bit more noise, or lower ratio is ok. If either my downstream or upstream signals degrade, I will see the correctable and uncorrectable errors start adding up faster than in the past. As you can (not) see my error counts are low and stay low... no spiking.