Charlie Wilkes <charlie_wilkes at easynews.com> wrote in message news:<dbdklv0gbjnn60j1sgstv94r7i0lc3rgo8 at 4ax.com>...
> More a priori science. Rocks can't fall from the sky, right?
In all fairness, Charlie, those calculations are easily verified, and
have been re-checked independently. I believe it's a very valid
argument against the claims of how the device works physically.
That's quite different from a scientific test of the claimed results
of the device. But that's what you've been planning to test, isn't
it? It's certainly something that we'd all like to see done. I'm
certainly more interested in verifiable results than the science
behind it and have no doubt that Mr. Howe doesn't really have the
scientific background to present the acoustic information accurately,
so will cut him some slack.
Lynn K.
>> I have been busy earning my living, but my hope is that I can get back
> to the cat shelter next week and continue my preparations for some
> genuine research.
>> Charlie
>> >This is WHY it cannot work:
> >
> >"After reading the web page for Jerry Howe's "little black box" and
> >doing a couple of calculations, I have demonstrated that the claims for
> >"Doggy Do Right" are physically impossible. Specifically, it cannot
> >possibly be audible to dogs at the ranges claimed.
> >
> >The essence of the reason is that attenuation of sound traveling through
> >the air is not uniform for all frequencies, but is strongly
> >frequency-dependent. The higher the frequency, the more rapid the
> >attenuation. Basically, the reason for this is that higher frequencies
> >require more rapid motion of the gas molecules which transport the
> >sound. More energy is used accelerating the molecules at higher
> >frequencies, causing more rapid attenuation (loss of signal). The
> >"Doggy Do Right" is claimed to be ultrasonic, i.e., to work by means of
> >very high frequency sound.
> >
> >Interestingly enough, the effect is not so pronounced in the frequency
> >ranges of typical human speech, music, etc. but can be observed. When
> >your neighbors, or passing motorists, play their stereos very loudly,
> >typically you hear only the bass, because the higher-frequency treble is
> >much weaker at any distance. When I was doing my postdoctoral research
> >in atmospheric physics at the Naval Research Laboratory in Washington,
> >DC, I used an acoustic levitator which pumped out many watts of sound at
> >33 kHz--an ultrasonic frequency, i.e. above the range of human hearing.
> >I was interested in applying to raise a CCI assistance-dog puppy at that
> >time, and was concerned about the effect of all of that noise (many,
> >many times the human pain and damage thresholds, except mercifully
> >silent to humans). 33 KHz is within the canine hearing range.
> >
> >To try to shorten a long story, both theory and measurements showed the
> >sound to be so rapidly attenuated that if the puppy remained by my desk
> >it would be unable to hear the ultrasonic source 18 feet away.
> >
> >The equation for sound attenuation as perceived by a measurement device
> >(or a dog) at some distance r (measured in meters) from a point source,
> >at room temperature, is
> >
> > I(source)*exp{-2E-13*(f^3)*r} I(dog) =
> >------------------------------ 4 * pi * r^2
> >
> >where r is the distance from the source to the dog; I(source) is the
> >intensity (power) output at the source; I(dog) is the intensity at the
> >dog, f is the frequency of the sound, and pi is the numerical constant
> >pi, approximately 3.14159265.
> >
> >This information may be found in almost any textbook on acoustics, but
> >we found it in "Sonics" by TF Hueter and RH Bolt, Wiley and Sons, 1955.
> >
> >Plugging in the frequency of 33 kHz replicated our measurements almost
> >exactly.
> >
> >So what does all of this imply for "Doggy Do Right"? It is claimed to
> >be "ultrasonic," meaning it must use frequencies above the range of
> >human hearing. We don't know if it emits a continuous monotone or some
> >varying pattern of frequencies, but it does not make any difference for
> >this demonstration. The range of human hearing is generally reported to
> >be 20-20,000 Hz (20 Hz - 20 kHz). Thus, in order to be "silent to
> >humans," as is claimed on the "Doggy Do Right" web page, the frequency,
> >or range of frequencies, used must be 20 kHz or higher.
> >
> >The greatest possible range would be obtained with the lowest possible
> >frequency, 20 kHz. Substituting this in for frequency in the equation
> >given above, we find that at room temperature the range of the device is
> >far less than the 500 ft claimed on the web site. It is less than 100
> >feet. I won't give the exact figure here, since it would be too easy
> >for Jerry Howe to simply adjust his claims to fit these results. Anyone
> >with a scientific calculator can repeat my calculation. I will mention,
> >however, that the range is so short that the device's claimed ability to
> >be heard by a dog across the street would not work in most
> >neighborhoods, with typical street widths and zoning (set back from
> >street) ordinances. If the frequency or frequencies used are higher
> >than 20 kHz, and/or the temperature is lower than "room temperature"
> >(which to physicists is about 77 Fahrenheit), the range will be even
> >less.
> >
> >For the purpose of the range calculation, I assumed that attenuation of
> >120 dB, or twelve orders of magnitude, would render the device
> >inaudible. This is the range in power between the human threshold of
> >hearing (minimum) and threshold of pain (maximum). While some believe
> >that dogs have a lower threshold of hearing than humans, that only
> >applies, if at all, within the range of best canine hearing, not at 20
> >kHz and above.
> >
> >For anyone who has read this far, my personal favorite line from the
> >Doggy Do Right web site is, "if you can hear barking dogs, they can hear
> >Doggy Do Right." My husband John, who has over 90% hearing loss, can
> >hear our hound Jobe (a.k.a. Ch. Gr. Nite. Ch. WC 'PR' Susquehanna Vally
> >Jobe) at distances over 2 miles, in the cold of winter. At that range,
> >at room temperature, the Doggy Do Right would be attenuated over 300
> >orders of magnitude.
