• 06-07-2007, 10:09 AM
    Rich-n-Texas
    Receiver White Noise vs frequency gen vs test CD
    Which one do you think will most accurately profile a room's acoustic properties? I still have room treatments/funishing to get into place, but I think white noise is not the best way to measure room acoutics. I have a 0 - 20MHz frequency generator at my disposal so I'll be able to cover the entire audible range, and we've determined that line level will be set at 1Vp-p on this generator. Someone mentioned that signal generators can wreak havoc with a system so what should I be mindful of if in fact using this method is a viable option? Thanks.
  • 06-07-2007, 06:28 PM
    canuckle
    Profile a room's acoustic properties? The tone's only purpose is to set levels. Either one will do fine for the task, don't make it harder for yourself. A frequency generator is a very good definition of needless overkill.

    The receiver and most calibration discs use pink noise, not white.

    0 - 20MHz takes you into the radio broadcasting range, lol :p
  • 06-08-2007, 04:19 AM
    Rich-n-Texas
    Quote:

    Originally Posted by canuckle
    Profile a room's acoustic properties? The tone's only purpose is to set levels. Either one will do fine for the task, don't make it harder for yourself. A frequency generator is a very good definition of needless overkill.

    The receiver and most calibration discs use pink noise, not white.

    0 - 20MHz takes you into the radio broadcasting range, lol :p

    40Hz - 22KHz = the audible range, which this generator is capable of producing and which is the point I was trying to make.

    Does the test tone have different reflective properties than the sound of a slide guitar, for instance? "Think pitch". I don't think a test tone has pitch does it?
  • 06-08-2007, 06:15 AM
    markw
    All in all, I'd say pink noise is a better test than a single tone.
    Instruments don't produce a single "tone". They do procuce a single fundamantal "tone", or note, and many, many harmonics as well. That's what gives each instrument it's unique sound.

    This is particularly troublesome with deep bass notes whose harmonics. along with the fundamantal, can excite many different room nodes.

    Now, if you've got the miscreant tones narrowed to one or two exact frequencies, then it might be useful in fine tuning.
  • 06-08-2007, 07:59 PM
    canuckle
    Quote:

    Originally Posted by Rich-n-Texas
    40Hz - 22KHz = the audible range, which this generator is capable of producing and which is the point I was trying to make.

    Does the test tone have different reflective properties than the sound of a slide guitar, for instance? "Think pitch". I don't think a test tone has pitch does it?

    Hopefully you can hear well below 40Hz. There's no way that you hear anywhere near 22KHz.

    Pitch and frequency are the same thing. The former is the musical term; the latter the scientific one.

    Still, it's all very irrelevant. The only purpose of using a test signal is to set the levels of the speakers so that they all play uniformly loud at the primary listening position. Pink noise is universally used because is contains all of the frequencies that we hear weighted according to how well we generally hear them. The channel balancing can do absolutely nothing about the reflective properties of a slide guitar so I'm failing to see the point of that reasoning (perhaps what you really want is an Audyssey-type of RoomEQ). You don't want the channels balanced for a slide guitar... you want them balanced for all sound that you can hear (aka: pink noise).
  • 06-09-2007, 07:02 AM
    emorphien
    Quote:

    Originally Posted by Rich-n-Texas
    40Hz - 22KHz = the audible range

    I highly doubt you can hear 20Khz, let alone 22. As we age our high frequency hearing worsens dramatically. You should however still be able to hear sound in the 20-40Hz range, and human hearing is generally considered to be about 20Hz to 20KHz, with the top end dropping off fastest.

    As far as pitch, look up your terms. Pitch is just a musicians way of referring to frequencies.
  • 06-09-2007, 07:28 AM
    Rich-n-Texas
    I was going from memory with those numbers from looking at receiver specs many years ago, but yes that's wrong. My HTR is spec'd @ 20Hz - 20KHz.

    I don't own a test CD but I can bring home a frequency generator from work at no cost to me. I can connect it to the front audio inputs with a BNC to RCA male & Y cable, which I already have; the generator has been preset with the right line level voltage, can be incremented in 1, 10 or 100Hz resolutions, so I figured why not?

    I'll just wait and see how things sound after room treatments are in place.

    Thanks for the replies. :thumbsup: