The perceived magnitude of sound.

The approximation of loudness is the perceptual correlate of the intensity of sound.

• Fletcher‐Munson equal loudness curves

– Created using a indirect method

– Phon scale

• Steven’s power function

– Created using a direct method

– Sone scale

Indirect method for measuring loudness: Alternating loudness balance

Listener adjusts Sound 2 until it sounds as loud as Sound 1 sounds in same ear.

Indirect method for measuring loudness:

Simultaneous loudness balance

Listener adjusts sound in right ear until it sounds as loud as sound in left ear.

• Set the level of a 1000 Hz tone

• Listener adjusts level of tone of other frequencies to sound equally loud

• A sound’s loudness, expressed on the phon scale, is the level in dB SPL of a 1000‐Hz tone that would sound equally loud.

• Example: – A 40 phon sound at 100 Hz sounds as loud as a 1000 Hz sound at 40 dB SPL

• Mid‐frequency range: equal dB SLs produce approximately the same loudness

• Note flat curves at high levels

• Loudness “grows” differently at very low frequencies

– Magnitude Estimation

– Magnitude Production

–(There are others)

Direct scaling procedures: Magnitude Estimation

• Listen to this sound and assign a number to it that reflects how loud it sounds to you (a standard)

• Now listen to this sound.

– If it sounds twice as loud to you as the first sound, assign it a number that’s twice as big.

– If it sounds half as loud to you as the first sound, assign it a number that’s half as big.

• That is, assign numbers according to a ratio scale

• May or may not give subject a standard sound to use as a comparison

• People are allowed to use whatever numbers they like, but when results are averaged, numbers are converted to a common scale.

– Subject instructed to adjust the level of a sound until it reaches some numerical value of loudness

• No standard given

• For example, “Adjust the sound until its loudness is 30.” OR… – Subject given a standard with an assigned number and is asked to adjust the intensity of a 2nd sound to some numerical value of loudness.

• For example, “The loudness of sound A is 100, adjust sound B until its loudness is 50.”

• Systematic relationship between loudness & level

• Note: log‐log coordinates

• A 10‐dB increase in level leads to a doubling of loudness

Magnitude Estimation Loudness Scale: Sone Scale

• Sone definition: – One sone equals the loudness of a 1‐ kHz tone at 40 dB SPL

• A sound that is 2x’s as loud = 2 sones, ½ as loud = 0.5 sone

Factors affecting loudness

1. Intensity

 2. Frequency

 3. Bandwidt

4. Duration

Factors affecting loudness: Frequency

• Equal loudness contours suggest that loudness does not grow at a uniform rate for all frequencies

– Loudness “grows” more rapidly at low frequencies than at mid frequencies

• At extremely high intensities, loudness is relatively independent of frequency

– Equal loudness contours are relatively flat at very high levels

Loudness growth for low‐vs.‐mid frequency

smaller changes in intensity necessary to change loudness by 10 phons at 100 Hz as compared to 1000 Hz

Loudness grows more rapidly at low frequencies

Factors affecting loudness: Bandwidth

Overall intensity is the same, bandwidth is increased

>200 Hz loudness grows more rapidly because larger bandwith

<200 Hz, they all sound the same

- For bandwidths less than the critical bandwith, if overall intensity is the same, changing the bandwidth had no effect.

- Once bandwidth exceeds the critical bandwidth, perceived loudness will increase even if overall intensity remains the same.

Factors affecting loudness: Duration

• Does the duration of the sound influence loudness?

– Yes! – For durations less than 250 ms, if the overall intensity of 2 sounds is the same, but they differ in duration, loudness will be different

– Example: a 100 ms sound will sound louder than a 10 ms sound even if their intensities are equal

Loudness adaptation

 - For very longdurations (seconds, minutes) loudness decreases over time

 -Biggest effect for high frequencies and low SLs