Hypersonic Speakers - Acoustic Heterodyning

i have been searching for any technical help regarding my project, hypersonic speakers,but my efforts were in vain. hypersonic speakers are instresting to work upon. kindly guide if if you have any knowledge regarding the topic

Mail from GA

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See these links ...

Hypersonic Sound: Sound From Thin Air - Mix two signals in a nonlinear medium and you'll end up with four - two at the original frequencies....

Hypersonic Sound speakers are like Invisible headphones.

Sound technology turns the way you hear on its ear - Woody Norris, inventor of ultrasound technology,

Acoustical Society of America Lay Paper on Hypersonic Sound: -

HyperSonic Sound HSS from American Technology Corporation employs ultrasonics to create audible sound in the air. It works by using harmless ultrasonic tones that we can't hear

More from Woody Norris - HyperSonic Sound. speaker

delabs

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Thanks for your reply for hypersonic speakers , but sir i am unable to have any positive feed backs as far as its making is concerned, i have contacted hypersonic industries also in this context, but they want me to buy a unit. i will see what i can do. thank you once again for your help.

Reply from GA

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I dont know if this idea is good for college projects, but you can buy a Hypersonic Speaker and demonstrate an application in automation.

delabs

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Lotte Graphic Equalizer - LG-920

Subject: delabs Schematic Source Request. Circuit: LG-920 Title: Lotte Graphic Equalizer Message:
Please send me a complete copy of the said equipment.

mail from JMB

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Go to this page ..... electronics.lotte-e.co.kr/front/pdf/pdf_audio1.asp.
On this page you will find LG-920 users manual. If you want service manual try eServiceInfo.com

delabs

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Graphic Equalizer Circuits

plz send me sound equalizer circuits.

post by AH

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go to google.com and enter this .......

graphic equalizer circuits and then press go. You have 1,200 pages to see, and the navigation for all the pages is at bottom of every page. anyway, i did it for you,

visit these links ................ Go online ...... and click these links.
mitedu.freeserve.co.uk/Circuits/Audio/3band.htm 3 Band graphic equalizer This circuit is similar to ones that used to come in Philips audio books, so try this first. Now to design your own, learn the technique here ... 4qdtec.com/graph.html A 10 band graphic equalizer from Sam. users.otenet.gr/~athsam/EQ_10_band.htm more here discovercircuits.com/A/au-tone.htm

delabs

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Noise and Hum in audio Circuits

i currently have a car stereo set that i use as an amplifier in my living room. but my main problem is that i a lot of noise hum when ever it is on especially when there happens to be a drop in the supply Voltage. i decided to use a voltage regulator and capacitor across (1600uF)...but it only reduced the hum a little. how can i completely eliminate the noise.

post by FP

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Ensure that the power supply has a full wave or bridge rectifier. If power supply transformer is say 12-0-12 two diodes must be there and a center tap ground OR If a square or round bridge is used with four leads or four diodes, then it is fine. Half wave rectification or a blown or leaky diode can cause this problem. Put all the filter caps you want and add a series choke as well the better the power supply the audio will be good.

The power supply transformer rating - voltage and current both may need to be boosted. Some very low budget transformers do not use CR-GO plates for lamination (i think it is Cold Rolled Grain Oriented ). They use plain thick metal plates without coating and hence hysteresis and eddy current both cause problems. Then you have ground loop hum and noise of semiconductors, the speaker ground and amplifier ground carry current and they should be directly connected to power supply ground, These you can understand by looking at these pages......

• hut.fi/Misc/Electronics/docs/groundloop/
• sound.westhost.com/noise.htm
• educypedia--audio.htm
• channld.com/hum.html

i am only aware of Phillips transistor based designs used 20 years back, but the above links have up to date info,

delabs

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Passive volume control

please if you don't mind I need to help to find a control circuit for volume of speaker 4 ohm or 8 ohm located in the another room far away of cassette or CD player by using only passive components with potentiometer without transformer.

mail from AD

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i have attached to this mail a simple circuit you can build at home at low cost. This is the only alternative for the need that you have specified. it uses just a rotary switch and wire wound resistors.

delabs

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