**Decibels**

**How to solve a decibel equation. **

Decibels are one of the most confusing units of measurement that we use. It’s not like other measurements in that it stays the same every time. It’s not a set size or distance . The thing you must understand is that a Decibel is a relationship between two values of power.

Generally the numbers that are being compared are of a vastly different magnitude.

Think of human hearing. You can hear your finger brush a paper as well as a gunshot. To compare the sounds to one another would be like comparing the softest audible sound (0.000000000001 watt/m2) to a sound that will actually cause pain in your ear (1 watt/m2).

The numbers are so far apart that we need a way to compare them that is easily understood. This is where Decibels come in.

If a sound is 10 times more powerful (10dB) than the original sound it sounds twice as loud. If we only double the power (3dB), the change might not even be noticeable.

*Decibels are a generally a ratio between units of power, intensity or amplitude. *

If the decibel is positive then the unit is increasing. 3dB means twice as big.

6dB = 2 x 2 = 4X the original

9dB = 2 x 2 x 2= 8X the original

20dB = 10 x 10= 100X the original

30dB = 10 x 10 x 10= 1000X the original

**Positive and Negative Decibel Conversion Table**

*Example 1. If Intensity or Amplitude has a factor of 4 = how many decibels? *

*Answer: 4 x **or** 2 x 2 = 6dB*

*Example 2. A reduction of intensity to 1/2 its original value is what in dB?*

*Answer: – 3dB*

*Example 3. -10dB means that the intensity is reduced to what portion of its original power?*

*Answer: 1/10*

## Ultrasound decibel practice exam

*Ultrasound decibel practice exam*.You scored %%SCORE%% out of %%TOTAL%%.Your performance has been rated as %%RATING%%

Question 1 |

Double | |

Increase 4x | |

Halve | |

Increase 10^2 |

Question 2 |

-6 | |

6 | |

3 | |

-3 |

Question 3 |

Increasing | |

Stays the same | |

Decreasing | |

Halved |

Question 4 |

3 | |

6 | |

9 | |

-9 |

Question 5 |

Decrease 10x | |

Increase 100x | |

Increase by 1/2 | |

Increase tenfold |

Question 6 |

Stays the same | |

Increasing | |

Halved | |

Decreasing |

Question 7 |

- 3dB | |

Negative | |

3dB | |

Positive |

Question 8 |

- 3dB | |

Negative | |

3dB | |

Positive |

Question 9 |

1/10 | |

1/100 | |

-10x | |

10x |

Question 10 |

-10x | |

10x | |

1/100 | |

1/10 |

List |

#### Franco

#### Latest posts by Franco (see all)

- Obstructive vs Nonobstructive Jaundice - June 26, 2014
- Intrahepatic Ducts vs Extrahepatic Ducts - June 25, 2014
- Period and Frequency equations - August 5, 2013

HI Mr Franco i will love to take classroom class to prepare ARDMS HOW CAN I FIND OUT WHERE TO CONNECT WITH YOU, I AM LIKE YOU Ultrasound is my passion, i had the chance to practice out the US for more than 12 years, now i am back, i need to take the test, i had see your videos and i live it, hope you can help me.

I have been talking with a few people about the best way to do some classroom training. Maybe either an online webinar for each exam topic? Still not sure what is the best way. I am in washington state so if I did do classes it would be up in the northwest.