noob needs help.... (amplify existing sound precisely15 decibels).

[mudbugII]

I need to amplify an existing sound by precisely15 decibels. I am unsure as to what type of device I need to do this. The existing sound will vary in intensity from 0 decibels up to about 60, but at any point in this range I need to be able to bump it 15 decibels higher than the existing setting.

Could any of you provide any assistance in what I would need to do this? The sound I am referring to would be just a buzzing sound or perhaps an electronic tone.

 

[blueroomelectronics]

What's it for?

 

[mudbugII]

i am trying to do a demonstration for a class that I teach about hearing loss. I want to utilize a buzzer or tone-type sound hooked to a volume control, the be able to boost the volume precisely 15 decibels by pushing a button. Short version, a 15 decibel loss in hearing is considered significant for reporting purposes and I want to show the difference between the two.

 

[blueroomelectronics]

Edit a wav file and set the gain at different points. Just play it back through an amplifier. Lots of audio editors out there, easier than building something.

I thought hearing loss was not normally linear and a good hearing aid had an equalizer.

 

[mudbugII]

I would like to do this without utilizing a computer; make it very portable and simple as possible. I was hoping that there was some type of resistor or capacitor that I could splice in between the volume control and the buzzer/mini speaker and use a single pole push button to intitialize. Also, you are absolutely correct that loss is not linear, it occurs and different frequencies at different rates, this is just a simple demo to show students and patients after I conduct their hearing tests and before we begin discussing hearing loss.

 

[blueroomelectronics]

Two 50K logarithmic pots with one end to the audio signal, the other end to gnd and the wiper (middle) one to each side of a SPDT switch with the center pin going to the amp should work. Trick will be calibrating their levels.
Still easier and more accurate to just use an MP3 player and a small amp.

 

[Jon Wilder]

Without knowing what your signal source is I doubt any of us could be of much help.

 

[Mikebits]

What is source and load impedance?

 

[Diver300]

Mike, the attenuator for 15 dB is fine, but when the switch is closed, the impedance will be far less than 8 ohms and will probably cause some attenuation.

The switch should be arranged so that when the attenuator is not wanted, it is not connected at all.

 

[Mikebits]

Yeah, I just realized that and deleted my erroneous post. Ya caught me before I could remove it Need to change the switch config. I posted correction in next post.

 

[Mikebits]

Okay, here is a 15dB attn. Assumes 8 ohm impedance.

 

[Noggin]

If this class is taught and graded, and you really want to get your point across, you should use a recording. Record a message and play it to your class at normal volume so that everyone can hear it. Tell them that you're going to simulate hearing loss and that anyone who can correctly hear the next message gets a bonus on a test or something like that. Drop the volume by the 15 dB and play a second and different message. To be fair, you should have everyone sit in a circle or something like that.

 

[audioguru]

A speaker is 8 ohms only at one frequency. It is about 40 ohms or more at resonance and since it is inductive then its impedance rises as the frequency rises.

I agree that most hearing loss that occurs over time is a loss of high frequency sensitivity because the person was exposed to loud sounds from guns or rock "music". A few people are born with hearing loss that is is a loss of all frequencies.

 

[Jon Wilder]

The source impedance governs the "current drive" of the source (i.e. how much current can be drawn from the source before the input to a circuit starts dropping the output voltage of the signal source). Example, if you have a signal source that is capable of sourcing 1mA of current at a 1V output, your source impedance would be 1K. If it was capable of sourcing 10uA @ 1V, the source impedance would be 100K. The less current it is capable of sourcing, the higher the source impedance.

The load impedance is either the impedance of the input to the device or the impedance of the load the device is driving on its output. In the case of an audio power amplifier, the latter of these would be the speaker impedance.

 

[blueroomelectronics]

I still think the a small MP3 player and portable amp would be the way to go. You could have several samples of audio at 0 & 15db attenuation. Easy.

 

[Externet]

Use an amplifier with voltage gain of 5.62 or power gain of 31.62 to obtain a 15 decibel increase.

 

[JimB]

Externet, please try to keep up old chap, this thread is three years old.

JimB