Wednesday, September 1, 2010

Are we using the right frequency speakers?

From James'blog:
"The frequency range of swiftlet echolocating calls is between 1-6 kHz, with most energy focused between 2-5 kHz (Fullard et al,. 1993). These frequencies fall into the range of normal human hearing. THERE IS NO ULTRASONIC COMPONENT (i.e., 20-160 kHz), which would be inaudible to people. (Cranbrook & Medway, 1965)"

Most tweeters claimed they can transmit 2-20 khz, somes are sold at 4 khz onwards.
If many birds flied into our house but refused to stay, one out of many reasons might be the wrong speaker!

We need to check the frequency of the sounds that come out from our speakers.
Even the tweeters claimed that it can produces sound at 2-20 khz, they do not!
Most of them produced from 4- 20 khz. Then the birds will only hear the sound from 4 khz onwards , which will not be a natural bird sound.

The right speakers should produce sound with frequency from 1 khz onwards.
But not many manufactures will produce speaker at this specification.
Because normal frequency range of tweeter is 2-20 khz, mid range will be 80 - 2000 hz., then the lowest frequency ones called woofer and sub woofer.
Shop carefully for the right tweeters.

Recently, I noticed through a CCTV observing my friend's new bird house that birds totally ignored the internal sound tweeter. Birds were more interested to all the external sound tweeters.
So we run a test to check the frequency of sound from both tweeters.

The picture below shows the frequency of sound recorded from his bird house internal sound speakers.
It showed that this tweeter delivered sound at frequency between 4000-9000 hz. Sound at below 4000 hz and higher than 9000 hz are very weak compared to the 4000-9000 hz range.


But for the below external sound tweeter that birds are crazy about it can deliver sound with the required frequency of 1400 hz upwards.

When compared the above graph with a graph obtained from a famous bird sound from a computer file, they are very similar that most sound are at at 1500-9000 Hz range. This means that this external tweeter can produce sound very similar to the original sound file from a computer.


After seeing the above and few more tests to confirm it, my friend decided to change all his speakers right away.
His bird house now has 360 birds staying within 85 days after operating.


  1. Hi,may I know which tweeter(brand name and model) that ur friend using now??

  2. Hi,

    We use local brand name (made in Thailand).
    You can use those made in your country, only the frequency spec. should at least cover the range from 1000 hz-15000 hz.
    Apart from the speaker spec, make sure you install and connect them correctly. Before and after installing , check the frequency of voice coming out from these speakers and compare.

  3. Hi
    can you please kindly let me known the name and model of the tweeter so that I do'nt have to trial an error.

  4. Hi,

    Both chart look similar, could you explain how you come to conclusion that external tweeter is better?
    What device you use to measure the frequency?
    Thank you.

  5. It would be great if you can inform the readers which tweeters (brand name & model) were yr friend using before he change . It may give unsuccessful BH owners some thing to ponder ! Thank you.


  6. It's just a normal piezo tweeter claimed to emit 1400 hz up.
    I don't want to put brand name here. I can be sued lah.

    The right frequency has been published since 1993. So if you all want to be successful, work a little bit harder in identifying the right frequency tweeter to be used in your Bird house.

    The most important thing for all newbies is "know the basic" and use it correctly. Don't listen to anyone or do anything blindly without asking " why?".

  7. It's a local brand here. I am not sure you can find it in your country. I really don't want to advertise for them publicly here.

    I concluded that the external tweeter was good because it delivered sound from frequency 1400 hz onwards similar to the original sound.
    While the internal tweeter only delivered sound from 4000 hz onwards. Birds heard nothing under 4000 hz. this made sounds that was unnatural to them. So birds were not interested to the internal tweeters we installed. After we changed to the new tweeters, we can see significant improvement.

  8. What software can i use to learn more about frequency?

  9. You can download it free, it is called "Audacity ". Search google.

  10. hi, i've been searching about what is the best setting sound for a swiftlet house? no one ever touch on that and here i am and i found your blog talking about frequency. Are u able to help me on how to tune best/frequency sound on the amp?

  11. First you need to check your speaker whether it's the right frequency one or not. By record the sound from your speaker and check it with Audacity program. If they give frequency from 3000 hz upwards. Then you need to do something.

  12. Hi, do you email add? would like to pm u.

  13. Give me yours, didn't like to disclose my e-mail here. Too many rubbish sent to me already.

    thank u.

  15. Not able to send mail to you, check your spelling.

  16. I think your graph not correct, you dont have detail of 1k to 6k graph. this is total not referable.

  17. I don't know what do you want to refer to?
    Can you show me how your correct or referable graph look like?

    All the above graphs started from 0-20,000 hz, why did you say no details from 1000- 6000 hz?