But first, just what is pitch in music? Whether you pluck a piano key or strum a guitar string or blow into a saxophone, that instrument produces a sound wave.
A sound wave is just vibrations of air molecules that go back and forth, creating a wave of pressure that travels from the instrument that produces the sound and is picked up by our ears. The main property of a sound wave is its frequency , which is just a word for how fast the cycle of the wave is. This is all a bit technical and mathematical, but just know that pitch is basically the frequency of a note. The higher the frequency, the higher the pitch and vice versa, the lower the frequency, the lower the pitch.
For example, a tone can have a pitch of Hz, which means the sound wave produced by the note repeats times in one second. The human ear can only hear tones with pitches between 20 Hz and 20, Hz, and almost all of the music you see and play would be between 50 Hz and 8, Hz. Same when you clap your hands or clink a fork to a glass of water, you are producing a tone with a pitch, but it is not necessarily a note.
A note refers to specific pitches, and in Western Music a note refers to one of 12 named tones that all music is made from — the notes of the chromatic scale.
If you are interested in music theory, you may want to further explore the relationship between pitch and musical scales. It is important to note that humans only hear sounds within a certain frequency range, but there are sounds outside of that range—and other species have more sensitive hearing and can detect sounds at higher frequencies. Dog whistles are a good example of a sound at a frequency 23 kHz to 54 kHz that humans cannot hear, but dogs can.
As you can see from these examples, familiar sounds fall within a wide range of frequencies. Once you start using the app to measure pitch, you may find many exciting ways to explore and compare pitch samples.
The Science Journal app uses the microphone that is built into your phone or mobile device to measure the pitch of sound. The app contains separate sensors to measure sound intensity and pitch. Both of these sensors use the microphone, and both pitch and sound intensity relate to what we hear or what the microphone hears.
But they are very different measurements. The sound intensity sensor is used to measure the intensity of sound which we may perceive as "loudness" , and it can measure low levels of sound or ambient noise. The pitch sensor measures the frequency of sound, and it is often used to measure the frequency of sustained sounds like humming or singing rather than sounds that are shorter in duration.
To measure or monitor pitch, open the app and start an experiment or open an existing experiment. Open the sensor tools by tapping the sensor icon on the gray toolbar and select the pitch icon looks like a musical note from the colored bar showing available sensors.
This will open a pitch sensor card. The image below shows a sample pitch sensor card. No data is being recorded in the card shown, but the sensor is actively monitoring sound reaching the microphone and measuring pitch. The graph on the sensor card shows the readings the sensor is making.
Note : A sensor begins reading as soon as a sensor card is opened, but the app only records data when you start a recording or take a snapshot reading. When viewing pitch sensor data, the units on the y-axis are in Hz. The x-axis represents time in mm:ss. Note : Remember that the x-axis does not show on iOS until a recording begins. A screenshot of a pitch sensor card in the Google Science Journal app. The sensor card is labeled and shows the name of the sensor at the top.
Below the name are icons to switch between sensors and below that is a graph for the sensor measured in Hz. Above the graph is an icon that shows the note of the current sound next to the pitch value of the current sound.
With a pitch sensor card open, say something out loud, and you will see the pitch of the sound on the graph. Try humming or singing instead. Experiment with single notes and with varied notes moving your voice up or down a musical scale, for example.
Your notes do not need to be perfect! As you hum or sing, you will see the changes in the pitch of your sounds show on the graph. As shown on the diagram above, the pitch sensor card also has a circular pitch icon that identifies the music note associated with the current pitch. This icon works like a tuner. It shows a dash - when there is no sound, but when sound is detected, the icon shows the closest musical note by letter and how flat low or sharp high the sound is.
The red dot on the outer ring of the icon indicates how close the pitch is to the natural note which is right in the middle of the ring. Using the Science Journal app, you can take snapshots of pitch readings or record changes in pitch over time. The image below shows how snapshots and recordings from the pitch sensor appear in the Science Journal experiment feed. Tapping a snapshot or a recording opens the observation so that you can view additional details or access additional features like crop and export for recordings.
A screenshot of a snapshot and recording taken from a pitch sensor card in the Google Science Journal app experiment feed. The snapshot shows a note and pitch value C and The recording shows a graph of the recording, the recording title, date and time, label for the sensor card and minimum, average and maximum values of the graph. When you open a recording from the experiment feed, you can review the graph in more detail.
A sample recording from the pitch sensor is shown below. A screenshot of a recording review for a pitch sensor card in the Google Science Journal app. A pencil at the top of the screen allows the user to rename the recording. Three dots in the top-right of the screen can be pressed to access additional tools such as cropping and sharing. The review shows the recording title, duration, date and time, and the type of sensor card used to record at the top of the screen.
The distance between one wave and the next gives the wavelength. For sounds all travelling at the same speed, high-frequency high-pitched sounds have waves very close together. Low-frequency sounds have a greater distance between each wave.
An extreme example is the low- pitch calls made by humpback whales, which can have up to metres between the pressure peaks of their sound waves. Frequency is measured in hertz Hz.
For sound, this means the number of pressure waves per second that would move past a fixed point. It is also the same as the number of vibrations per second the particles are making as they transmit the sound. A sound of 10Hz means that 10 waves would pass a fixed point in 1 second. Sound travels at a speed of metres per second in air or 1, metres per second in water. Humans can normally hear sounds between 20Hz and 20,Hz 20kHz.
Noise is a very subjective term. When the sound waves form a single sine-shaped wave on a graph, we hear the sound as a pure note.
Tuning forks produce a pure sound, one note a single frequency and a very smooth line on a graph. When we combine pure notes, we can create harmonics. Harmonics are the basis of all musical instruments and result from overlaying pure notes.
The trace on the graph is bumpy and random. Our ears detect this as a less pleasant sensation and often try to screen it out. In terms of listening under water, what we mainly hear is noise — a jumbled mess of sounds with no repeating pattern or clear pure notes.
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