开启你的智能生活Perception Neuron 动作捕捉
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NEURON品类：标签：印象：易安装简单好用便携式设计感强科技感炫酷操作灵活【产品介绍】Perception Neuron是由诺亦腾公司推出的一款动作捕捉系统，系统内设有小巧的模拟神经元网络Neuron，你可以将它放在任何自己想放的位置，并通过USB或WiFi将动作数据输入到电脑中，获得最为精准的仿真效果。Perception Neuron动作捕捉系统，旨在让捕捉技术变得更加便捷和便宜。Perception Neuron的用途很广泛，可用于各种不同应用中的视觉效果(VFX)领域，包括游戏互动、虚拟现实、动作分析、医药学分析和实时的舞台表演等。你可以将它们放在任何你想放的位置，无论是手上、身体上，亦或是其他物体，也正因为它的轻便，你可以做各种想做的动作。硬件参数官方价格：1499美元链接方式：WiFi搭载平台：Windows/Mac/UNITY/Oculus VR可选颜色：黑色佩戴方式：手套/头戴适配机型：iOS/Andirod分享到:扫一扫手机阅读、分享文本
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Perception Neuron(TM) Makes Professional Motion Capture Adaptable and Extremely Affordable
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Beijing-based Noitom Ltd. revolutionizes the motion capture industry with the smallest, most versatile and adaptable wireless system, at a price that makes the technology affordable for anyone. Starting at USD $200, the company is launching its campaign on Kickstarter and unveiling production prototypes to the industry at SIGGRAPH in Vancouver.
Perception Neuron Complete System
We built a professional system that outperforms most costing hundreds of thousands more.
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will create a small revolution as it unveils its (TM) Motion Capture system to computer and interactive graphic professionals attending the annual
conference in Vancouver. Touted as one of the smallest, most versatile and adaptable system ever designed, affordability is one of the biggest “wow” factor. With pricing starting a US$ 200, Perception Neuron is redefining an industry that is used to price tags in the tens of thousands.
Perception Neuron was developed on four precepts— size, adaptability, versatility and affordability. The system is based on interchangeable motion sensors called Neurons, each about 1cm x 1cm that connect to a Hub. A Hub can connect from 1 to 30 Neurons. The adaptability of the Perception Neuron system allows the wearer to move the individual Neurons where you need them — on a hand for detailed movement, anywhere on the body for full body capture or even on accessories. This level of customization is groundbreaking. The systems is also ready to go out of the box as it comes with software development kits for Unity, Windows, OSX and Oculus Rift in addition to open source games. Perception Neuron can either be operated via WIFI or USB and it is powered by any USB power pack.
“Although making Perception Neuron accessible to everyone was one of our four precepts, we built a professional system that outperforms most, hundreds of times more expensive,” explains Tristan Dai, CTO and co-founder of Noitom. “Motion capture has not evolved much over the years and it has remained the playground of big studios and even bigger budgets. We want to change that paradigm and allow all the creative minds out there access to this amazing technology. I think we will see people use Perception Neuron in ways we have not yet even imagined.”
Perception Neuron is being launched as a Kickstarter campaign. 10-Neuron packages start as low as USD$ 200 with 30-Neuron Packages topping at USD $550. “Kickstarter was our platform of choice for the launch because it is a global community of makers, forward thinkers and creative individuals,” explains Haoyang Liu, CEO and co-founder of Noitom. “We felt this was the perfect environment to showcase Perception Neuron because we know that its use and function go well beyond what we have imagined — and this is the community of people that will come up with a thousand new and innovative ways to make Perception Neuron come to life.”
Perception Neuron is on display and being demoed at the Noitom booth (#533) at SIGGRAPH Vancouver from Tuesday August 12 to Thursday August 14 at the Vancouver Convention Center. Media is invited to come by the booth or contact our media coordinator at noitom(at)myrockgroup(dot)com. Media kits are also available by requesting them from the media coordinator.
About Noitom
Founded in 2011, Noitom Ltd. works with a team of dedicated engineers who develop world-class motion capture technology for consumer and commercial markets through the integration of MEMS sensors, pattern recognition, human kinetics and wireless transmission. Noitom is an international leader in innovative technology for use in animation, film, medical applications, robotics and gaming. Noitom is headquartered in Beijing with affiliate offices in Shenzhen. For further information about Noitom and its services, please visit, . For general inquiries, please email, info(at)noitom(dot)com.
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@noitomocapPerception Lecture Notes: Frequency Tuning and Pitch Perception
Perception Lecture Notes: Frequency Tuning and Pitch Perception
Professor David Heeger
What you should know from this lecture
Frequency tuning, decomposition of sound by the cochlea
Characteristic frequency
Auditory (8th) nerve
Place code theory
Temporal code theory
Cochlear microphonic
Volley principle
Phase locking
White's cochlear implant experiments
Virtual pitch
Shepard's pitch illusion
Frequency Tuning
von B&k&sy used linear systems theory and Fourier
analysis to
characterize the motion of the basilar membrane. He found that the
basilar membrance acts
as a shift invariant linear system (by testing shift-invariance, the
and superposition). He then used sinusoidal stimuli (pure tones) to
the frequency response at different points along the basilar membrane.
then was able (using linear systems theory) to predict the response
is, the motion of the basilar membrane) for any sound.
This is a schematic diagram of the uncurled cochlea. The cochlea is
homogeneous piece of tissue. It varies in thickness and elasticity as
it curls from the
oval window out to the helicotrema. The effect of this is that
different parts
of the basilar membrane respond more strongly to some sounds than
For sinusoidal (pure tone) sounds, each point on the basilar membrane
oscillates
up and down at the same frequency as the sound. What differs from point
point is the size of the oscillation.
This figure shows the displacement of the basilar membrane over time, in response to a pure tone stimulus. Some points are displaced up and others down. Over time, the different points on the membrane move up and down (indicated by the 3 curves in the bottom panel of the figure). The entire motion that occurs on the basilar membrane in response to a sound stimulus is called a traveling wave. Each point moves up a different points move up and down slightly delayed (out of phase) with respect to one another, yielding the traveling wave. The wave begins at the oval window, rises to a crescendo somewhere along the basilar membrane, and finally falls off with the energy being absorbed around the helicotrema. The dashed lines indicate the envelope of the membrane modulation, the maximum excursion of that bit of membrane throughout the duration of the traveling wave.
This movie shows a simulation of the travelling wave motion along the basilar membrane, again in response to a pure tone stimulus.
Envelope for several frequencies
Each point along the basilar membrane oscillates a different amount,
on the frequency of the sound. Points near the oval window, at the
oscillate the largest amount in response to high frequency tones.
near the helicotrema oscillate by the largest amount in response to
frequency tones.
This graph shows the location of peak excursion for different tone frequencies. These measurements were made on post mortem human ears. This simply summarizes what I've already said. The location of the biggest oscillation depends in a systematic way on the frequency of the tone.
The reason for the appearance of the travelling wave along the
basilar membrane is the fact that the stimulus begins with a push at
the oval window, which forces the part of the cochlea nearest the oval
window to begin oscillating, and then it takes time for that
oscillation to propagate down the length of
the cochlea. The reason that the travelling wave peaks at one location
because the different points of the basilar membrane oscillate by
different amounts - different amplitudes - in response to different
tone frequencies.
But what about sounds that are not simple pure tones. Becuase the motion of the basilar membrane behaves like a shift-invariant linear system, we can readily predict its motion in response to a complex sound, just by knowing its motion in response to pure tones. The motion in response to a complex sound is just the sum or the responses to the pure tone components of that complex sound.
This animation (make sure to have the volume up high enough to hear the sound track) shows a simulation of the basilar membrane for some complex sounds.
Each auditory nerve fiber is connected to a small number of hair cells, near one another, on the basilar membrane. The nerve fiber's response is governed, therefore, by the motion of a small region of the basilar membrane. And the basilar membrane in any small region undergoes its largest motion only for a limited range of frequencies.
This graph plots the sensitivities of each of three auditory nerve fibers, in response to pure tones of different frequencies. The horizontal axis plots the frequency of the input stimulus. The vertical axis plots the threshold stimulus intensity, the minimum sound pressure level (in dB) needed to evoke a response. Notice that each neuron is most sensitive over a narrow range of frequencies (about 700 Hz, 1300 Hz and , near 10,000 Hz). The most sensitive frequency for an auditory nerve fiber is called the neuron's characteristic
frequency. Different auditory nerve fibers attach to different portions of the basilar membrane. The nerve fiber with characteristic frequency of 10,000 Hz must be connected to the section of the basilar membrane near the oval window because it is tuned to very high frequencies. The nerve fiber with characteristic frequency of 700 Hz must be attached near the helicotrema.
Summary: The representation of information on the basilar
membrane and in the 8th nerve is very different from the representation
at the tympanic membrane. The tympanic membrane displaces to a 100 hz
tone, a 1000 hz tone, and to a 10,000 hz tone. It responds to all
auditory stimuli, come what may,
and faithfully reproduces the changing air pressure by a displacement.
watching any part of the tympanic membrane, we can discriminate between
By the time we have reached the cochlea and beyond, the physical
signal is no longer represented by a single mechanism. Rather, we now
have forty thousand mechanisms - the 8th nerve fibers coming from the
cochlea to the brain - which each encode different portions of the
stimulus. And each component
is deaf to most of the range of auditory frequencies. This
decomposition of
the response into different neural channels is very similar to what we
with the swinging pendulum. There are lots of motions that cause no
whatsoever in the long pendulum. From its point of view, it is as
nothing is happening.
Place and Temporal Code Theories of Pitch Perception
Pitch is a perceptual attribute, not a property of the physical
stimulus. In a loose and imprecise way, the pitch we perceive is
related to the frequency of the sound.
Place Code Theory: Helmholtz's theory of pitch is based on observations of the anatomy of the ear. It has been the most important theory of hearing for 100 years. Sensation of a low frequency pitch derives exclusively from the motion of a particular group of hair cells, while the sensation of a high pitch derives from the motion of a different group of hair cells. Each sensation is perfectly identified with the action of an anatomical location along the basilar membrane. The place code theory is given that name because it identifies each pitch with a particular place along the basilar membrane. It assumes that any excitation of that particular place gives rise to a specific pitch.
This figure shows an illustration of how place code theory relates to what we have learned about the frequency tuning in the cochlea. For a low frequency tone (top row), the largest motion is at
position 1 along the basilar membrane. Hence, there are action potentials in auditory nerve fibers connected to position 1. For a high frequency tone, the largest motion is at position 2 so there are action potentials in auditory nerve fibers connected to position 2.
Temporal Code Theory: According to temporal code theory, the location of activity along the basilar membrane is irrelevant. Rather, pitch is coded by the firing rates of nerve cells in the audotry nerve. In principle, this makes a lot of sense. A low frequency tone causes slow waves of motion in the basilar membrane and that might give rise to low firing rates in the auditory nerve. A high frequency tone causes fast waves of motion in the basilar membrane and that might give rise to high firing rates.
This figure shows an illustration of how temporal code theory relates to the cochlea. Both the low and high frequencies evoke responses at both positions, but there are more action potentials in response to the high frequency.
However, there's a problem with temporal code. The ear is sensitive
frequencies from about 20 Hz up to 20,000 Hz. But a single nerve cell
not signal at a rate of 20,000 Hz. Therefore, the possibility of a
code accounting for the detection of the pitch of a 20,000 Hz tone
impossible
because no nerve cells can conduct that many impulses per second. And,
fact, Hallowell Davis, in the 1930s, showed that the maximum response
of auditory neurons in the cat is about 1000 action potentials per
Cochlear Microphonic: The cochlear microphonic is a discovery
that cast doubt on
Helmholtz's place
code and supports the temporal code theory. It was discovered by Wever.
The cochlear
microphonic
is a small electrical signal that can be measured by an electrode
near the hair cells of the cochlea. We now know that the cochlear
microphonic
arises from the sum of electrical potentials in the hair cells of the
cochlea. It mimics the form of the sound pressure waves that arrive at
frequency tones result in low frequency modulations of the cochlear
microphonic
electrical signal. High freq tones result in high freq modulations of
electrical signal. Combinations (sums) of high plus low frequency tones
in sums of high and low frequency modulations in the cochlear
microphonic
electrical
signal. In fact, the cochlear microphonic is a shift-invariant linear
that obeys the scalar, additivity, and shift-invariance rules.
Volley Principle: The volley principle reconciles the fact that the cochlear microphonic mimics the sound pressure waves with the implausibility of the temporal code. Wever suggested that while one neuron alone could not carry the temporal code for a 20,000 Hz tone, 20 neurons with staggered firing rates could. Each neuron would respond on average to every 20th cycle of the pure tone, and the pooled neural responses would jointly contain the information that a 20,000 hz tone was being presented.
Phase Locking is an empirical observation that supports the volley principle.& When auditory nerve neurons fire action potentials, they tend to respond at times corresponding to a peak in the sound pressure waveform, i.e., when the basilar membrane moves up. The result of this is that there are a bunch of neurons firing near the peak of each and every cycle of a pure tone. No individual neuron can respond to every cycle of a sound signal, so different neurons fire on successive cycles. Nonetheless, when they do respond they tend to fire together.
Why is phase locking important? What you need (for temporal code
theory, and to explain the cochlear microphonic) is for the neural
activity to look
just like the sound pressure waveform. The response (across the whole
population
of hair cells/8th nerve fibers) must follow each rise and fall of sound
level in the sound signal.
Wever's temporal code theory (based on the volley principle) was a
clear rejection of Helmholtz's Place Code Theory, and it was backed up
by compelling data (cochlear microphonic and phase locking). Wever said
that the particular neuron that was signalling was not important, but
instead, the way in which the neurons signalled together contained the
information as to the pitch of
the sound.
How might you test thest two alternative hypotheses? Discussion...
White's Cochlear Implants: Professor John White of the
electrical engineering Department at Stanford did some experiments that
directly addressed these 2 alternative hypotheses. The ultimate goal of
his research was to produce
cochlear implants to make up for some kinds of hearing loss. There are
such diseases, including one fairly common one called Meniere's
disease, that can poison and destroy the hair cells in
inner ear, while leaving the auditory nerve and the rest of the
system intact. What we would like to do for these patients is to send a
directly to the auditory nerve that will effectively substitute for the
that the auditory nerve would be receiving were the system fully
White's early experiments with cochlear implants were designed to
test the place and temporal code theories of pitch perception. White
implanted four electrodes located at different positions along the
basilar membrane. He tested the two theories by delivering different
types of electrical stimuli
to his observer and asking the observer to estimate the pitch of the
delivered by the prosthetic device. He varied the signal in two ways.
he varied which of the four electrodes was used for stimulation. By
the dependence of pitch on which electrode was being stimulated he
test the place code theory. Second, White varied the rate of the
electrical
stimulation. He stimulated either with a low frequency series of
electrical
through one of the electrodes, or with high frequency series of pulses
the same electrode. By measuring the dependence of pitch on the
of electrical stimulation he could test the temporal code theory.
As it turns out, both mechanisms play a role in pitch perception. As
stimulating frequency is increased, the subject tends to report a
higher pitch.
This continues over a significant range, up to a maximum of about 300
At that point, the rate of stimulation on the electrode does not seem
influence the subject's judgement. The perceived pitch also depends on
electrode was doing the stimulating, i.e., the place that is being
stimulated
is also important information.
In fact, this makes sense. Place coding is weak below 300 Hz because
a broad pattern of oscillation of the basilar membrane at low
frequencies
back at the figure near the beginning of the lecture showing the
of basilar membrane motion for low frequencies). The temporal code
at low frequencies because fibers can phase lock most easily for low
frequencies.
Caveat: the patient reported that these electrical stimulations did
sound particuarly like tones, but rather they sounded like a noisy kind
buzzing. The buzzing could appear to be at different pitches. But it
nonetheless, a buzz rather than a clear tone with a distinct pitch.
Virtual Pitch
Construct a sound that is made by adding pure tones with frequencies
800, 1200, and so on. The 400 Hz component is called the base or fundamental
frequency of the tone complex, and the other frequencies are called
higher harmonics. Most sound sources (your vocal tract, musical
instruments)
produce sounds like this. The higher harmonics come along for the ride.
Imagine that you perform the following experiment. Present the tone complex pictured in (a), then present a pure tone, and ask the observer to set the frequency of the pure tone so that its pitch matches the frequency of the tone-complex. This is an example of a matching
experiment.
The perceived pitch of this tone complex is very much the same as a pure tone with the same fundamental frequency (400 Hz). Next repeat this experiment using the tone complex pictured in (b) which has a fundamental frequency of 800 Hz and harmonics at multiples of that fundamenatal (1600 Hz, 2400 Hz). The perceived pitch of this tone complex is again the same as a pure tone with the same fundamental frequency (800 Hz this time).
Now take the original tone complex with 400 Hz fundamental and harmonics and remove (subtract out) the 400 Hz component, as pictured in (c). The lowest frequency is now 800 Hz, so you might think that perceived pitch of this new tone complex would match that of an 800 Hz pure tone. Surprisingly, observers still match the complex with a pure tone of 400 Hz.
This is a challenge to Helmholtz's place theory because the tone complex in (c) does not contain any energy that would stimulate the auditory nerve at the point where a tone of 400 Hz would stimulate the nerve. If pitch is encoded by position alone, then how can these two yield the same pitch? This is also a challenge to Wever's volley theory, because there is no energy (or oscillation) in the tone complex at 400 Hz, i.e., there is no 400 Hz component in the cochlear microphonic. Both the place theory and the temporal code/volley theory play roles in pitch perception. However, neither theory provides a complete explanation of pitch perception. Even though it is a seemingly simple perceptual attribute, pitch is not currently fully understood.
If you shift the tone complex to higher frequencies (e.g., from 400,
1200,... up to 500, 900, 1300,...) it is perceived at a slightly higher
Note that this manipulation is a bit odd in that the tones of the new
are no longer exact harmonics of 400 Hz or any frequency near 400 Hz.
The auditory system
them as "nearly harmonic'' and identifies/assigns a virtual pitch.
Roger Shepard and others having taken advantage of residual pitch to
an auditory illusion that gives the sensation of a sound that
continuously changes in pitch, rising or falling forever.
The intensity of each component is specified by an amplitude
envelope that
tapers off at very high and low frequencies.The frequency components
then shift upward gradually, increasing in frequency over time, but
with the amplitude of each component constrained to be that specified
by the fixed, non-shifting envelope. As a result, the low frequency
tones gradually increase in
amplitude and the high frequency tones
gradually decrease in amplitude, as they all shift up in frequency.
one tone falls off the top (note that its amplitude has been reduced to
by then), a new one is added down at the bottom (initially with zero
amplitude,
but gradually increasing). The result sounds like it is rising in pitch
forever, but never manages to get much higher than where it started,
much like an M. C. Escher print.
Copyright & 2006, Department of Psychology, New York University
