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As an overview, low frequency (or tone) sensorineural hearing loss (LF SNHL or LT SNHL) is unusual, and mainly reported in Meniere's disease as well as related conditions such as low CSF pressure.
Le Prell et al (2011) suggested that low frequency hearing loss was detected in 2.7% of normal college student's ears. Oishi et al (2010) suggested that about half of patients with LTSNHL developed high or flat hearing loss within 10 years of onset. The new international criteria for Meniere's disease require observation of a low-tone SNHL. Gatland et al (1991) reported fluctuation in hearing at low frequencies with dialysis was common, and suggested there might be treatment induced changes in fluid or electrolyte composition of endolymph (e.g.
Although OAE's are generally obliterated in patients with hearing loss > 30 dB, for any mechanism other than neural, this is not always the case in the low-tone SNHL associated with Meniere's disease. The lack of universal correspondence between audios and OAE's in low-tone SNHL in at least some patients with Meniere's, suggests that the mechanism of hearing loss may not always be due to cochlear damage. Of course, in a different clinical context, one might wonder if the patient with the discrepency between OAE and audiogram might be pretending to have hearing loss. Papers are easy to publish about genetic hearing loss conditions, so the literature is somewhat oversupplied with these. Bespalova et al (2001) reported that low frequency SNHL may be associated with Wolfram syndrome, an autosomal recessive genetic disorder (diabetes insipidus, diabetes mellitus, optic atrophy, and deafness). Bramhall et al (2008) a reported that "the majority of hereditary LFSNHL is associated with heterozygous mutations in the WFS1 gene (wolframin protein). Eckert et al(2013) suggested that cerebral white matter hyperintensities predict low frequency hearing in older adults. Fukaya et al (1991) suggested that LFSN can be due to microinfarcts in the brainstem during surgery. Ito et al (1998) suggested that bilateral low-frequency SNHL suggested vertebrobasilar insufficiency. Yurtsever et al (2015) reported low and mid-frequency hearing loss in a single patient with Susac syndrome. There are an immense number of reports of LTSNHL after spinal anesthesia and related conditions with low CSF pressure.
Fog et al (1990) reported low frequency hearing loss in patients undergoing spinal anesthesia where a larger needle was used. Waisted et al (1991) suggested that LFSNHL after spinal anesthesia was due to low perilymph pressure. Wang et al reported hearing reduction after prostate surgery with spinal anesthesia (1987).
We have encountered a patient, about 50 years old, with a low-tone sensorineural hearing loss that occured in the context of a herpes zoster infection (Ramsay-Hunt). LTSNHL is generally viewed as either a variant of Meniere's disease or a variant of sudden hearing loss, and the same medications are used. Voltage-to-frequency converter circuits are used not so much to produce oscillations but rather to measure volt­ages precisely.
For sinusoidal oscillators, the presence of a resonant circuit imposes a limited tuning range. To increase the tuning range, different component val­ues can be switched around for different ranges. Although their frequency can be varied only over a very small range, crystal oscillators can change frequencies dra­matically by switching the crystal element. Relaxation and ring oscillators have wide tuning ranges in spite of their poor stability and noise performance. Ring oscillators are a popular topology for variable fre­quency oscillators used in integrated circuits because they have broad tuning range and require no resonators.
When a tuned circuit is used to define the oscillation fre­quency, it is desirable to preserve its frequency selective properties Q. Figure 7 shows two ways of looking at how an amplifier can be connected across a tank circuit using capacitive di­vision of voltage. A single transistor implementation of the capacitively divided tank circuit is depicted in Fig. Tuned oscillators may also use transmission lines, cavi­ties, dielectric resonators, crystals, or YIG resonators to de­termine their operating frequency. A general way of thinking about an oscillator is in terms of an amplifier that feeds its output back to its own input (Fig. Normally, for oscillation to start, the active device provides more energy than is being dissipated in the resonator. The requirements for oscillation are that the amplitude of the signal being fed back be large enough to produce an output that can reproduce the feedback (greater than unity loop gain) and that the relative phase between the input and the fed-back input be near zero (so the feedback reinforces the output). The Creative Aurvana Gold Wireless are solidly built but uncomfortable headphones, and have a focus on features rather than on audio reproduction. Not the most lightweight headphones out there, but the main issue is the stiffness of the pads. How the headphones are designed to prevent them from slipping off your ears or falling off your head. If you plan on using the headphones while doing sports or other physical activities that requires a lot of movement.
When the material is heavy on bass frequencies, such as those of kick drums and bass guitar.
The amount of deviation (weighted standard error) in bass frequency response (20Hz-250Hz) as compared to a target response that would sound perfectly balanced to most people.
The amount of deviation (weighted standard error) in mid frequency response (250Hz-2.5KHz) as compared to a target response that would sound perfectly balanced to most people.
When the material is heavy on high-range frequencies, such as voice, cymbals, and any other material where brightness, brilliance and airiness is desired.
The amount of deviation (weighted standard error) in treble frequency response (2.5KHz-20KHz) as compared to a target response that would sound perfectly balanced to most people.
When clean and pure sound reproduction is desired, though its effect is not as noticable as frequency response.
A bulldozer that is idling (presumably dozing, not actively bulling) is loud enough at 85 dB to cause permanent damage after only 8 hours. When listening to music on earphones at a standard volume level 5, the sound generated reaches a level of 100 dB, loud enough to cause permanent damage after 15 minutes! A clap of thunder from a nearby storm (120 dB) or a gunshot (140-190 dB, depending on the weapon), can both cause immediate damage.
When damage first occurs, it usually affects the part of the ear sensitive to the mid-frequency range of 3 to 5 kHz. Hearing loss may or may not be accompanied by tinnitus – a ringing, buzzing or fluttering in one or both ears. For positive value of , it could be seen that corresponding to the linear up and down motion, the natural whirl frequency remains constant. It can be solved in two ways (i) Take a value of A and solve fourth degree polynomial equation in , or (ii) Take a value of and solve a linear equation in , i.e. To us, this seems a little overly stringent, compared to the earlier 1995 AAO criteria that just required any kind of hearing loss, but criteria are better than no criteria. That being said, genetic conditions should not be your first thought when you encounter a patient with LTSNHL.
One would think that diabetes insipidus is so rare that hearing loss is probably not the main reason these individuals are seeking attention.
These patients are extremely rare because there isn't much microsurgery done close to the brainstem.


We are dubious about the conclusion of this paper because it is different than nearly every other paper in the literature. We are dubious that this has any applicability to humans and we have never seen a patient with lithium toxicity with any LFSNHL.
We have observed this occasionally ourselves, but of course, the usual pattern is a conductive hyperacusis. We find this somewhat plausible as pregnancy and delivery might be associated with spinal anesthesia, with changes in collagen, and with gigantic changes in hormonal status. They achieve linear transfer characteristics from voltage to frequency and allow a frequency counter (a digital circuit of high repeatability) to measure the in­put voltage level. 19, the input voltage Vin causes current to flow into the precision integrator cir­cuit containing or including Ci. Detailed schematic of a Schmitt-trigger oscillator with the single timing capacitor tied to ground. This is a desirable feature because producing a variable voltage is usually easier than producing a vari­able current.
Frequency change in these circuits usually uses variable capacitors—or vari­able resistors in an RC oscillator.
In some radios, channels are changed by switching crystal values in sev­eral oscillators, and their outputs are multiplied or mixed together to produce the desired frequency.
It is easy to tune them over a 10:1 ratio, and with careful circuit design, more than two decades of frequency control are possible.
Depending on speed, tuning range, and method of tuning required, a variable-frequency oscilla­tor that meets the required needs can be found. It consists of an amplifier with a positive feed­back connection that causes hysteresis in the multivibra­tor.
16 is a popular oscilla­tor circuit that is often built in university engineering lab­oratories and by hobbyists. Other possibilities are changing the power supply voltage or the value of the collector load resistors, which are typi­cally smaller than R2 and R3. They consist of a number of amplifiers or delay stages that may be inverting or noninverting, connected in such a way that an odd number of inversions exist around the loop (Fig.
One popular way is to change the internal delay of each buffer by adjusting the amount of current available to charge and discharge the circuit capacitances.
This causes the amplitude of the oscillation to grow until it is limited by changes in the active device that reduce its gain.
More simply said, the one-way trip around the loop needs to have gain greater than one and zero phase. Additionally, stable oscil­lations develop only if disturbances in amplitude or phase cause the oscillator to respond by moving back to the un­stable point. They are easy to pair wirelessly and offer decent isolation but drastically skew the audio profile by overamplifying the bass. The thick brown headband and circular ear cups are highlighted by silver and black accents.
They may soften-up with use, or you may get used to them with time, but they are not comfortable out of the box. The plastic doesn't seem to be the best out there, but it is better than what you get with most headphones.
They pack a punch in the low end but the over-emphasized bass and dip in the mid-range causes vocals and lead instruments like guitars to sound weak. To make the score more perceptually relevant, more weight is given to the higher frequencies. The rise in distortion at 100 dB SPL is mostly in the mid and low regions, except for the peak at 5.5KHz. While normal hearing people may also have tinnitus, it is usually symptomatic of some sort of high frequency hearing loss. A new patent reveals that the next iPods and iPhones could automatically count how long a person has been listening and at what volume, before gradually reducing the sound level. It is worthwhile to diminish the number of parameters as much as possible by the dimensional analysis. For a shaft with simple supports and a disc at the mid-span, such a case is possible as shown in Figure 5.29. Whereas, for tilting motion corresponding to the forward whirl it increases and for backward whirl it decreases. There is a large literature about genetic causes, mainly in Wolfram's syndrome ( diabetes insipidus, diabetes mellitus, optic atrophy, and deafness), probably because it is relatively easier to publish articles about genetic problems.
He defined LTSNH as that the sum of the three low frequencies (125, 250, 500) was more than 100 dB, and the sum of the 3 high frequencies (2, 4, 8) was less than 60 dB. In other words, Wolfram's is probably not diagnosed mainly by ENT's or audiologists, but rather by renal medicine doctors, as DI is exceedingly rare, while LTSNHL is not so rare in hearing tests.
That being said, it is very rare to encounter any substantial change in hearing after pregnancy.
However, as an example of a variable – frequency oscillator, this is the most linear of all. The comparator with hys­teresis periodically switches capacitor Cf from the voltage reference Vref to the input terminal of the integrator, dis­charging it fully. Even if the frequency control is by variable capacitance, varactors that require a control voltage can be used. In the past, mechanically tuned air dielectric capacitors and even variable inductors were used. Mechanical switches have been used in the past, but today switching diodes are preferred because of their small size, lower cost, and higher frequency perfor­mance (less parasitics).
Voltage-to-frequency converters are also easy to tune over broad ranges, although they are relatively slow oscillators.
Of course, no single oscillator can simultaneously satisfy all possible needs, and other variables like available materials and costneed to be evaluated.
When one of the inputs causes the output to swing in one direction, the positive feedback changes the switching threshold, reinforcing the input so that there is no hesita­tion if the input begins to change back. It is nonlinear because the two transistors take turns being on and off, without spending much time midway. The system has two stable points: when Q1 is on and when Q1 is off (and Q2 is therefore on).
The dif­ferential amplifier and two emitter-followers on the right are connected in positive feedback. Several types of impedance transformation are possible by using cou­pled inductors, inductive division, or capacitive division. Capacitors C1 and C2 in se­ries form part of the resonator, and the input loading by the amplifier is reduced by their ratio. The feedback in the Hartley circuit is provided by inductive division, using two inductors or a single inductor with a tap connection.
For example, because of the interaction between voltage and mechanical resonance, piezoelectric quartz crystals are much more stable and of higher Q than LC resonators. The feedback is controlled by a resonator or a delay element in such a way that the desired frequency and am­plitude of oscillation are achieved.
The losses in a system may be linearly related to its am­plitude over a limited region, but they grow more rapidly (nonlinearly) over an extended region of amplitude, until they eventually hard limit the amplitude (e. Finally, reliable oscillators need to have only one frequency at which the conditions for oscillation are met; otherwise, frequency jumps could occur. The similarly designed Aurvana Platinum has the same esthetic but a brighter color scheme that may be more appealing to some.


If your listening habits involve a lot of lead instruments, vocals and require a lot of clarity in the mid or high notes, then you will be disappointed with what the Aurvana Gold has to offer. The under-emphasized high-mids negatively affect the presence and forwardness of vocals and lead instruments. This is the region responsible for clarity and intelligibility of vocals and most instruments.
Unfortunately, they leak a lot of sound, making it easy for others to hear what you are listening to at high volumes. It should be noted that these kind of uncoupling of the linear and angular motions is a special case with = 0A and in general such uncoupling of motions is not possible and for such systems all natural frequencies both the linear and angular motions would be present with different relative magnitudes and directions.
For A -, the frequency curve is symmetric with respect to = 0 line, which means the natural frequency does not depend upon the direction of rotation of the symmetric rotor. Roughly speaking, the frequency patterns of hearing loss are divided up into: Low-frequency, mid-frequency, high-frequency, notches, and flat. This achieves the transfer of a measure of charge in a way that is independent of the waveform driv­ing the switch, as long as capacitor Cf is given enough time to discharge fully. In cases where the control variable is naturally current, as in relaxation oscillators or in some ring oscilla­tors, a voltage-to-current converter can be added to make the circuit a VCO. When transistor Q1 turns on, its col­lector pulls the base of Q2 down, through C2, keeping it off.
When the transistor di­rectly on top of the timing capacitor is turned on, it quickly charges it to near the power supply voltage and forces the “trigger” to switch states. Transistors Q1 and Q2 form a cross-coupled pair through Q3 and Q4 that acts like an emitter-follower buffer. The loop is therefore never “happy,” and the result is that an “edge” propagates around the loop. If the amplifier is inverting, then the RC network needs to produce 180° of phase shift at the frequency of oscillation.
Another possibility is to use another amplifier as a buffer: the input impedance of the buffer is high, and the loading on the resonator is light. The circuit on the left uses the capacitors as a way of getting 180° of phase shift at resonance, while internally completing the loop with an ad­ditional 180° resulting from signal inversion. Inductive division, using two inductors or a single inductor with a tap connection, provides the feedback in the Hart­ley circuit. The value of the collector load resistor needs to be large enough to prevent decreasing the Q of the resonant circuit. Its output is directly coupled to its nonin­verting input, and therefore the feedback needs to provide 0° of phase delay because 360° would be impossible with the circuit shown. Note that the resonator or delay box is still indicated as a two-terminal box with another two-terminal amplifying box connected across it. The only redeeming qualities are the padded headband and the position of the control buttons. For the zero speed the four natural frequencies is reduced to two = ±1, which is really one frequency only because = +1A corresponding to the forward whirl and = -1A corresponding to the backward whirl and the non-rotating shaft can not distinguish the forward and backward whirls. Note that the polarity of Vref needs to be opposite that of Vin, or the capacitor needs to be discharged inverted. However, the tuning range is limited to less than an octave in a resonant circuit that uses variable components.
This prevents noisy outputs when the inputs are changing too slowly or when they “sit” too close to the threshold. This turns off the top transis­tor, and the current source begins to discharge the capaci­tor linearly. In this configura­tion, when one of the two bottom transistors is on, it forces the other transistor off and vice versa, in a “latching” ar­rangement with large hysteresis. Loops with as little as two buffers are possible, but for large number of stages it is customary to choose prime numbers to prevent the oc­currence of multiple modes of oscillation. Stated differently, the oscil­lation will occur at that frequency at which the feedback has a phase delay of 180° and the gain is greater than one. However, the two capacitors are still connected in series to each other and across the inductor, and voltage division takes place across this tank.
At resonance, the LC tank presents a purely resistive load to the collector output, and therefore it has no phase delay.
This can be done by connecting the top side ofthe capacitor to the input, and the switch to the bottom side. When no current flows through the p-i-n diode, the i-layer acts like a thick dielec­tric, and the diode’s capacitance is low. In the case of this oscillator, the hysteresis allows the operation of the circuit, which would not occur otherwise.
For example, if we used six buffers, we could have three “edges” running around the loop, with the result that the frequency would sometimes be three times higher.
Other possibilities to realize the phase delays are to RL (resistor-inductor) delay or lossy transmission line delay. The advantage of capacitive division over inductive division is that it is easier to realize in an in­tegrated circuit. The Armstrong circuit uses two inductors, L1 and L2, with in­ductive coupling between them. This arrangement can be modified by placing a capacitor in series with the coil (and providing base bias). Any internal delay through the device will need to be canceled by adjusting the oscillation frequency slightly out of resonance. The R and C connected to the inverting input cause this point to vary exponen­tially up and down around the hysteresis voltage region. As Q2 turns on, it will turn Q1 off, and as the collector of Q1 goes high, it will reinforce Q2 being on. The output wave­forms of this oscillator consist of narrow complementary pulses, whereas the voltage across the timing capacitor is a linear sawtooth waveform. The transistor that is on must supply current to both cur­rent sources I and therefore will begin to charge capacitor C until the voltage at its own emitter rises and turns it­self off. This may be attractive if the objective is to keep the input and output biases isolated from each other.
The series resonant frequency of the coil and the added capacitor can dominate the oscillation frequency, making the circuit less sensitive to variations in the transistor and in the other two capacitors. The frequency of this oscillator would normally be controlled by using a variable capacitor. From equation (5.78), it can be seen that for the present case the second forward critical speed (for ) would not be feasible and only the second backward critical speed (for ) would be .
Moreover, the amount of coupling between the coils can be varied without changing the values of the inductors. The RC time constants (R2C1 and R3C2) need not be the same, and nonsymmetrical os­cillations can be designed with this circuit. The other transistor begins to charge the capacitor in the opposite direction, and the cycle repeats itself. A small change in frequency can also be obtained by changing the bias on the differential amplifier.



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