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What is the difference between the velocity operated and pressure operated microphones?
Know your microphones - what is the difference between pressure, pressure gradient, and velocity microphones?
David Mellor | November 30, -0001
Microphones work on the principle of pressure, pressure gradient, or velocity. If you don't know the difference, then you can't yet call yourself a sound engineer.
This is something from the text books. Actually you don't have to know this to be a sound engineer - the proof of that is the 90% of sound engineers that don't know it! Yet a little theory never hurt anyone. And if you know how things work in theory, then you can apply them better in practice.
There are two basic types of microphone - omnidirectional and figure-of-eight, which can be made in either dynamic or capacitor forms. Cardioid and hypercardioid microphones are hybrids, combining features of both the omni and figure-of-eight.
The omnidirectional microphone works on the pressureprinciple. The diaphragm, which picks up sound vibrations in the air, is completely open at one side, but completely closed at the other.
The sound vibration is either pushing the diaphragm against the fixed pressure of the air on the other side, or it is reducing the pressure on the front of the diaphragm allowing the pressure behind to push it out.
One of the features of pressure in a gas is that it pushes equally in all directions. "Equally in all directions"? That makes the mic omnidirectional then.
[For the sake of completeness, it should be mentioned that there is a tiny hole in the capsule to the rear of the diaphragm. This is so the microphone can compensate for long-term variations in air pressure. The hole is too small to affect its sound characteristics.]
The figure-of-eight microphone on the other hand has both sides of the diaphragm fully open to the air. So it doesn't compare the incoming sound pressure with a fixed pressure on the other side of the diaphragm like the omnidirectional microphone. Instead it compares the pressure of the sound wave on one side with the pressure of that same sound wave after it has traveled through to the other side.
Yes, it is a tiny difference in pressure, but strong enough to move the diaphragm.
The difference in pressure between the front and the back of the diaphragm depends on the angle of incidence of the sound wave. In the extreme, if the sound arrives from the side of the diaphragm, then the pressure will be the same at the front and the rear, therefore the diaphragm will not move and there will be no output.
Lastly, the velocity microphone... it doesn't exist! However you will see the term used frequently, particularly in relation to ribbon microphones.
A velocity microphone, if it existed, would respond to the actual velocity of the air molecules striking the diaphragm.
For this to happen though, the diaphragm would have to be so light that it could respond almost instantaneously, and so thin that there was no pressure difference between the two sides of the diaphragm. In practice, the diaphragm is too heavy to acquire the velocity of the air molecules and it has significant thickness.
But a microphone that doesn't make it as a velocity mic, because its diaphragm is too heavy and thick, is still sensitive to pressure gradient. So in practice, these microphones are pressure gradient mics.
So now you know it - the difference between pressure, pressure gradient and velocity microphones.
What else can I help you with?
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Superficial velocity is nothing but the velocity of a fluid in a pipe,conduit,column etc in the absense of packing or obstruction. like in packed columns the actual velocity of the fluid through it is actually the volumetric flow rate divided by the cross sectional area. so the velocity achieved by the same fluid in the same column in absence of the packing is called superficial velocity.
What is the working principle of convergent-divergent nozzle?
A NOZZLE IS A DUCT WHICH CONVERT HEAT ENERGY INTO KINETIC ENERGY.IT INCREASES VELOCITY OF FLUID PASSING THROUGH IT ,AT THE EXPENCE OF PRESSURE. STEAM EXPANDS IN NOZZLE FOLLOW RANKINE CYCLE.FLOW THROUGH NOZZLE IS ISENTROPIC. mritunjay04@gmail.com
Is it possible for an objects velocity to be perpendicular to the objects acceleration?
no
How is hydraulic grade line effected by increased distance to the water pump station?
The hydraulic grade line will drop over distance due to friction loss in the pipe. For example if you had 10m of 100mm pipe and the water was flowing at 8.71 liters per second at a velocity of 1.185 meters per second you would lose 1.317 kilo pascals of pressure.
Define Velocity of propagation for co-axial cable?
The velocity factor is the speed at which an RF signal travels through a material compared to the speed the same signal travels through a vacuum. The velocity of propagation is inversely proportional to the dielectric constant. Lowering the constant increases the velocity.Generally, the higher the velocity factor, the lower the loss through a coaxial cable.General Rules for Coaxial CableD = diameter of insulation under the shieldd = diameter of inner conductor.Velocity Factor, Velocity of Propagation, VpThe higher the velocity factor, the lower the loss through the cable.Raising the D/d has no effect on VpRaising the dielectric constant lowers VpCapacitanceRaising the D/d ratio lowers capacitanceRaising the dielectric constant raises capacitanceImpedance Raising the D/d radio raises impedanceRaising the dielectric constant lowers impedanceAttenuation or LossRaising the D/d ratio lowers attenuationRaising the dielectric constant raises attenuationSo in simpler terms the larger amount of dielectric between the center conductor and sheath equals less loss in RF. Trunk cables have less loss than feeder legs.
What is the difference between velocity and pressure on flowing fluid?
velocity is a distance travelled per sec
What is the Difference between Dynamic pressure and static pressure?
Dynamic pressure is the pressure exerted by a fluid in motion, caused by its velocity, while static pressure is the pressure exerted by a fluid at rest. Dynamic pressure increases with the square of the velocity, whereas static pressure remains constant regardless of velocity.
What is the difference between velocity pressure and static pressure in fluid dynamics?
Velocity pressure is the pressure exerted by the movement of a fluid, while static pressure is the pressure exerted by the fluid when it is not in motion. In fluid dynamics, velocity pressure is related to the speed of the fluid flow, while static pressure is related to the fluid's potential energy.
What is the difference between static pressure and velocity pressure in fluid dynamics?
Static pressure in fluid dynamics refers to the pressure exerted by a fluid at rest, while velocity pressure is the pressure associated with the movement of the fluid. Static pressure is uniform in all directions within a fluid, while velocity pressure increases with the speed of the fluid flow.
How does a pitot tube utilize the principles of Bernoulli's equation to measure fluid flow velocity?
A pitot tube uses Bernoulli's equation to measure fluid flow velocity by comparing the pressure difference between the stagnation point and the dynamic pressure of the fluid. This difference in pressure is used to calculate the velocity of the fluid flowing past the pitot tube.
How do you get cfm with a manometer?
To calculate CFM (cubic feet per minute) using a manometer, measure the pressure difference across a restriction in the airflow system. Use the manometer reading and the area of the restriction to determine the velocity pressure. Then, use the velocity pressure to calculate the airflow in CFM using the formula CFM = (Velocity Pressure * Area of the Restriction) / 4005.
What is a velocity microphone?
A velocity microphone is a sensor whose electric output depends on the velocity of the air particles that form a sound wave . Examples are a hot-wire microphone and a ribbon microphone (bi-directional).Velocity-sensitive microphones also respond much more to wind noise than pressure sensitive microphones (omnis). You get heavy bass tip-up or proximity effect if the sound source is close to the microphone. Cheers ebs
Can static pressure be converted to velocity pressure?
Yes, static pressure can be converted to velocity pressure through the Bernoulli's equation, which relates total pressure to the sum of static pressure and dynamic pressure (velocity pressure). In a flow system, the dynamic pressure represents the kinetic energy of the fluid due to its velocity, while static pressure is the pressure exerted by the fluid when it is at rest.
How do you find the average velocity pressure?
To find the average velocity pressure, you would need to calculate the total velocity pressure and divide it by the number of measurements taken. This would give you the average velocity pressure over the measurement period.
As the pressure gradient increases wind velocity increase decrease or remains the same?
As the pressure gradient increases, the wind velocity increases. This is because a larger pressure gradient indicates a greater difference in pressure between two points, leading to a stronger force exerted on the air. This stronger force results in faster wind velocities.
What is the effect on velocity and pressure if a liquid flows in a convergent pipe?
I think velocity is directly proportionate to its applying pressure.
What happens to the pressure gauge reading if the flow velocity is increased?
From the Bernoulli equation, pressure drop increases with the square of velocity. So if the velocity is doubled the pressure drop will increase by a factor of four.
